Add integration test of qiskit-sphinx-theme (Qiskit#960)

Closes Qiskit#715.

This is useful generally for better testing of our conversion pipeline,
as it's our only test that tests the entire conversion pipeline.

It also is useful to allow us to easily compare Sphinx's behavior vs.
our app's behavior, like the PDFs I uploaded in
Qiskit#947.

--

I didn't document this in the README because we don't talk about testing
in the README currently. Our README is already quite long, so I was
hesitant to add to it since most technical writers don't care about
testing, unlike Jupyter notebook testing that we do document.

Instead, I documented the test file itself. I'm not sure if this is
clear enough.

---------

Co-authored-by: Arnau Casau <47946624+arnaucasau@users.noreply.github.com>

.prettierignore

@@ -1,2 +1,3 @@
 docs
 translations
+scripts/lib/api/testdata

scripts/lib/api/__snapshots__/conversionPipeline.test.ts.snap

@@ -0,0 +1,378 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`qiskit-sphinx-theme: _package 1`] = `
+"{
+  "name": "qiskit-sphinx-theme",
+  "version": "0.1.1"
+}
+"
+`;
+
+exports[`qiskit-sphinx-theme: _toc 1`] = `
+"{
+  "title": "Qiskit Sphinx Theme",
+  "children": [
+    {
+      "title": "api_example",
+      "children": [
+        {
+          "title": "Overview",
+          "url": "/api/qiskit-sphinx-theme/module"
+        },
+        {
+          "title": "Electron",
+          "url": "/api/qiskit-sphinx-theme/api_example.Electron"
+        },
+        {
+          "title": "my_function",
+          "url": "/api/qiskit-sphinx-theme/api_example.my_function"
+        },
+        {
+          "title": "SimpleInlineClass",
+          "url": "/api/qiskit-sphinx-theme/inline_classes"
+        }
+      ]
+    },
+    {
+      "title": "Release notes",
+      "url": "/api/qiskit-sphinx-theme/release-notes"
+    }
+  ],
+  "collapsed": true
+}
+"
+`;
+
+exports[`qiskit-sphinx-theme: api_example.Electron 1`] = `
+"---
+title: Electron
+description: API reference for api_example.Electron
+in_page_toc_min_heading_level: 1
+python_api_type: class
+python_api_name: api_example.Electron
+---
+
+# Electron
+
+<span id="api_example.Electron" />
+
+\`api_example.Electron(size=None, name=None)\` [GitHub](https://github.com/Qiskit/qiskit_sphinx_theme/tree/stable/0.1/api_example/electron.py "view source code")
+
+Bases: \`object\`
+
+A representation of an electron.
+
+**Examples**
+
+\`\`\`python
+from api_example import Electron
+
+ELECTRON = Electron(size="2GB", name="QuantumComputing")
+\`\`\`
+
+Create an electron.
+
+**Parameters**
+
+*   **size** (*str*) – How big should this thing be?
+*   **name** (*str*) – The name we’ll call the electron. Nicknames preferred.
+
+**Raises**
+
+**ValueError** – You did something wrong
+
+## Attributes
+
+<span id="api_example.Electron.CLASS_ATTRIBUTE" />
+
+### CLASS\\_ATTRIBUTE
+
+\`= re.compile('abc')\`
+
+<span id="api_example.Electron.charge" />
+
+### charge
+
+<span id="api_example.Electron.mass" />
+
+### mass
+
+The mass of the electron.
+
+<span id="api_example.Electron.really_long_named_attribute_that_probably_does_not_fit_nicely" />
+
+### really\\_long\\_named\\_attribute\\_that\\_probably\\_does\\_not\\_fit\\_nicely
+
+A bit too verbose if you ask me.
+
+## Methods
+
+### compute\\_momentum
+
+<span id="api_example.Electron.compute_momentum" />
+
+\`compute_momentum(velocity)\`
+
+Compute the electron’s velocity.
+
+**Parameters**
+
+**velocity** (*float*) – The electron’s velocity
+
+**Returns**
+
+The computed momentum.
+
+**Raises**
+
+**ValueError** – You did something wrong
+
+**Return type**
+
+float
+
+### method\\_with\\_a\\_reallyyreallreallyreallyreallyreallyreallreallyreallyreallyreally\\_long\\_title
+
+<span id="api_example.Electron.method_with_a_reallyyreallreallyreallyreallyreallyreallreallyreallyreallyreally_long_title" />
+
+\`method_with_a_reallyyreallreallyreallyreallyreallyreallreallyreallyreallyreally_long_title()\`
+
+blahblahblahblahblahblahblahblahblahblahblahblahblahblahblahblahblahblah
+
+### overloaded\\_func
+
+<span id="api_example.Electron.overloaded_func" />
+
+\`overloaded_func(arg1: tuple[str, str], arg2: list[str], arg3: int, arg4: Electron) → None\`
+
+\`overloaded_func(arg1: tuple[int, int], arg2: list[int], arg3: bool, arg4: set[Electron]) → None\`
+
+This is meant to test out [https://github.com/Qiskit/qiskit\\_sphinx\\_theme/pull/319](https://github.com/Qiskit/qiskit_sphinx_theme/pull/319).
+
+**Parameters**
+
+*   **arg1** – Tuples ftw!
+*   **arg2** – But lists are more flexy.
+*   **arg3** – Primitive values are good too.
+*   **arg4** – Recursionnnnn.
+
+"
+`;
+
+exports[`qiskit-sphinx-theme: api_example.my_function 1`] = `
+"---
+title: my_function
+description: API reference for api_example.my_function
+in_page_toc_min_heading_level: 1
+python_api_type: function
+python_api_name: api_example.my_function
+---
+
+<span id="api-example-my-function" />
+
+# api\\_example.my\\_function
+
+<span id="api_example.my_function" />
+
+\`api_example.my_function(input1, input2, input3=None, **kwargs)\` [GitHub](https://github.com/Qiskit/qiskit_sphinx_theme/tree/stable/0.1/api_example.py "view source code")
+
+A function that does awesome stuff.
+
+**Returns**
+
+Did the function work.
+
+**Raises**
+
+*   **ValueError** – If the inputs are not the correct values.
+*   **TypeError** – If the inputs are not strings.
+
+**Return type**
+
+int
+
+"
+`;
+
+exports[`qiskit-sphinx-theme: inline_classes 1`] = `
+"---
+title: SimpleInlineClass
+description: API reference for api_example.inline_classes.SimpleInlineClass
+in_page_toc_min_heading_level: 1
+python_api_type: class
+python_api_name: api_example.inline_classes.SimpleInlineClass
+---
+
+# Inline classes
+
+This is a page to test out how we render classes and functions included inline in the page. This is common with module pages.
+
+## Important APIs
+
+Every time you use this program, you’ll want to create an instance of [\`api_example.inline_classes.SimpleInlineClass\`](#api_example.inline_classes.SimpleInlineClass "api_example.inline_classes.SimpleInlineClass"). It has a simple interface:
+
+<span id="api_example.inline_classes.SimpleInlineClass" />
+
+\`api_example.inline_classes.SimpleInlineClass(arg1)\` [GitHub](https://github.com/Qiskit/qiskit_sphinx_theme/tree/stable/0.1/api_example/inline_classes.py "view source code")
+
+This is a simple class that does not have any methods or attributes.
+
+It only has the class description and constructor. Many classes in Qiskit docs are simple like this.
+
+It can be useful to use free functions rather than the class:
+
+###
+
+\`api_example.my_function(input1, input2, input3=None, **kwargs)\` [GitHub](https://github.com/Qiskit/qiskit_sphinx_theme/tree/stable/0.1/api_example.py "view source code")
+
+A function that does awesome stuff.
+
+**Returns**
+
+Did the function work.
+
+**Raises**
+
+*   **ValueError** – If the inputs are not the correct values.
+*   **TypeError** – If the inputs are not strings.
+
+**Return type**
+
+int
+
+Sometimes, you even need to use a really complex class!
+
+<span id="api_example.inline_classes.InlineClassWithMethods" />
+
+\`api_example.inline_classes.InlineClassWithMethods\` [GitHub](https://github.com/Qiskit/qiskit_sphinx_theme/tree/stable/0.1/api_example/inline_classes.py "view source code")
+
+Bases: \`object\`
+
+This class is more involved.
+
+Note how the methods and attributes are rendered and indented when this class is inlined on the docs page.
+
+## Attributes
+
+<span id="api_example.inline_classes.InlineClassWithMethods.CLASS_ATTRIBUTE" />
+
+### CLASS\\_ATTRIBUTE
+
+\`str\`
+
+\`= 'An important part of any API.'\`
+
+<span id="api_example.inline_classes.InlineClassWithMethods.interest_rate" />
+
+### interest\\_rate
+
+## Methods
+
+### method1
+
+<span id="api_example.inline_classes.InlineClassWithMethods.method1" />
+
+\`method1()\`
+
+A simple method.
+
+**Return type**
+
+int
+
+### method2
+
+<span id="api_example.inline_classes.InlineClassWithMethods.method2" />
+
+\`method2(arg1, arg2, description)\`
+
+A method with a lot of args!
+
+This method will use a Hamiltonian to reach quantum advantage. Hamilton: great play & the secret to quantum computing. What a polymath.
+
+**Parameters**
+
+*   **arg1** (*int | float*) – All numbers accepted.
+*   **arg2** (*list\\[*[*InlineClassWithMethods*](#api_example.inline_classes.InlineClassWithMethods "api_example.inline_classes.InlineClassWithMethods")*]*) – A list of other instances, although these will be discarded.
+*   **description** (*str*) – If your description is too boring or too cryptic, this program will crash your computer.
+
+**Return type**
+
+tuple\\[int, [*InlineClassWithMethods*](#api_example.inline_classes.InlineClassWithMethods "api_example.inline_classes.InlineClassWithMethods")]
+
+### Warning: exceptions
+
+The above APIs might raise an exception! Be careful!
+
+### CustomException
+
+<span id="api_example.inline_classes.CustomException" />
+
+\`api_example.inline_classes.CustomException\` [GitHub](https://github.com/Qiskit/qiskit_sphinx_theme/tree/stable/0.1/api_example/inline_classes.py "view source code")
+
+See how exceptions render too.
+
+## Other prose
+
+Blah blah blah.
+
+"
+`;
+
+exports[`qiskit-sphinx-theme: module 1`] = `
+"---
+title: api_example
+description: API reference for api_example
+in_page_toc_min_heading_level: 2
+python_api_type: module
+python_api_name: api_example
+---
+
+<span id="api-example-api-example" />
+
+<span id="module-api_example" />
+
+# API example
+
+<span id="module-api_example" />
+
+\`api_example\`
+
+Welcome to my super cool module!
+
+<Admonition title="Note" type="note">
+  This is an example!
+</Admonition>
+
+Testing internal references… [\`Electron.compute_momentum()\`](api_example.Electron#compute_momentum "api_example.Electron.compute_momentum").
+
+## Contents
+
+|                                                                                               |                                     |
+| --------------------------------------------------------------------------------------------- | ----------------------------------- |
+| [\`Electron\`](api_example.Electron "api_example.Electron")(\\[size, name])                      | A representation of an electron.    |
+| [\`my_function\`](api_example.my_function "api_example.my_function")(input1, input2\\[, input3]) | A function that does awesome stuff. |
+
+## Functions
+
+###
+
+\`api_example.my_function(input1, input2, input3=None, **kwargs)\` [GitHub](https://github.com/Qiskit/qiskit_sphinx_theme/tree/stable/0.1/api_example.py "view source code")
+
+A function that does awesome stuff.
+
+**Returns**
+
+Did the function work.
+
+**Raises**
+
+*   **ValueError** – If the inputs are not the correct values.
+*   **TypeError** – If the inputs are not strings.
+
+**Return type**
+
+int
+
+"
+`;