Add indentation to API docs

[Eric-Arellano]

See https://www.figma.com/file/sNXucK1uMaZ8XXyLTZrdrs/OneDocs?type=design&node-id=4918-32646&mode=design&t=eQXKiDCRAEETmXbh-0

There are a few levels of indentation going on:

• code objects like methods and attributes are indented relative to their containing class
• within each code object, like a method, the specific contents are indented.

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Pay attention to how we implement #735, using a <div> vs MDX component. We'll need to auto-compute the indentation levels I think and set the appropriate HTML class.

[Eric-Arellano]

We added indentation to functions/methods and are happy with how it looks:

Note that we don't indent the same as the original issue, where the subsections like Returns are further indented. Doing that is actually fairly complex because it would require having structured data—such as a new MDX component—for the web app to know how to indent properly. Something like <Returns>content</Returns>, or <Function returns="content">. That is challenging to do reliably and risks many edge cases.

We think the status quo is sufficient. If we decide otherwise, we can reopen this issue or a new one.