feat: Add gatsby-theme-emma-core (#49)

Basically the same process as:
gatsbyjs/gatsby#16166

> A Gatsby theme for creating a blog child theme. It includes all of the data structures you need to get up and running building a blog and includes no additional theming or style opinions.

Just for the Emma theme. Which means:

You can totally customize the design now, but keep the data structure. So awesome <3
As the Theme UI styling for example happens in `emma`, not `emma-core`.

.eslintrc.js

@@ -67,7 +67,7 @@ module.exports = {
     "import/extensions": 0,
     "react/jsx-one-expression-per-line": 0,
     "react/no-danger": 0,
-    "react/display-name": 1,
+    "react/display-name": 0,
     "react/react-in-jsx-scope": 0,
     "react/jsx-uses-react": 1,
     "react/forbid-prop-types": 0,

plop-templates/theme/gatsby-config.js.hbs

@@ -8,7 +8,6 @@ module.exports = themeOptions => ({
     siteLanguage: `en`,
     siteImage: `/banner.jpg`,
     author: `@lekoarts_de`,
-    basePath,
   },
   plugins: [
     `gatsby-plugin-typescript`,

themes/gatsby-theme-emma-core/.npmignore

@@ -0,0 +1,17 @@
+.cache
+node_modules
+public
+projects
+
+.idea
+.vscode
+.DS_Store
+
+index.d.ts
+types.ts
+
+__tests__
+
+
+tsconfig.json
+jest.config.js

themes/gatsby-theme-emma-core/README.md

@@ -0,0 +1,79 @@
+<p align="center">
+  <a href="https://themes.lekoarts.de">
+    <img alt="Gatsby Theme" src="https://img.lekoarts.de/gatsby/gatsby-themes-illustration.png" />
+  </a>
+</p>
+<h1 align="center">
+  @lekoarts/gatsby-theme-emma-core
+</h1>
+
+<p align="center">
+  <a href="https://github.com/LekoArts/gatsby-themes/blob/master/LICENSE">
+    <img src="https://img.shields.io/badge/license-MIT-blue.svg" alt="@lekoarts/gatsby-theme-emma-core is released under the MIT license." />
+  </a>
+  <a href="https://www.npmjs.org/package/@lekoarts/gatsby-theme-emma-core">
+    <img src="https://img.shields.io/npm/v/@lekoarts/gatsby-theme-emma-core.svg" alt="Current npm package version." />
+  </a>
+  <a href="https://npmcharts.com/compare/@lekoarts/gatsby-theme-emma-core?minimal=true">
+    <img src="https://img.shields.io/npm/dm/@lekoarts/gatsby-theme-emma-core.svg" alt="Downloads per month on npm." />
+  </a>
+  <a href="https://npmcharts.com/compare/@lekoarts/gatsby-theme-emma-core?minimal=true">
+    <img src="https://img.shields.io/npm/dt/@lekoarts/gatsby-theme-emma-core.svg" alt="Total downloads on npm." />
+  </a>
+  <img src="https://img.shields.io/badge/PRs-welcome-brightgreen.svg" alt="PRs welcome!" />
+  <a href="https://twitter.com/intent/follow?screen_name=lekoarts_de">
+      <img src="https://img.shields.io/twitter/follow/lekoarts_de.svg?label=Follow%20@lekoarts_de" alt="Follow @lekoarts_de" />
+    </a>
+</p>
+
+Core Theme for [`@lekoarts/gatsby-theme-emma`](https://github.com/LekoArts/gatsby-themes/tree/master/themes/gatsby-theme-emma). This theme implements the `Project` and `Page` node interfaces and exports templates (+ queries) which you can shadow.
+
+[**Demo Website**](https://emma.lekoarts.de) ([Source Code](https://github.com/LekoArts/gatsby-starter-portfolio-emma))
+
+Also be sure to checkout other [Free & Open Source Gatsby Themes](https://themes.lekoarts.de)
+
+## Installation
+
+```sh
+npm install @lekoarts/gatsby-theme-emma-core
+```
+
+## Usage
+
+### Theme options
+
+| Key            | Default Value      | Description                                                                                               |
+| -------------- | ------------------ | --------------------------------------------------------------------------------------------------------- |
+| `basePath`     | `/`                | Root url for the theme                                                                                    |
+| `projectsPath` | `content/projects` | Location of projects                                                                                      |
+| `pagesPath`    | `content/pages`    | Location of additional pages (optional)                                                                   |
+| `mdx`          | `true`             | Configure `gatsby-plugin-mdx` (if your website already is using the plugin pass `false` to turn this off) |
+
+The usage of `content/pages` is optional. If no page/MDX file is found the navigation will be hidden.
+
+#### Example usage
+
+```js
+// gatsby-config.js
+module.exports = {
+  plugins: [
+    {
+      resolve: `@lekoarts/gatsby-theme-emma-core`,
+      options: {
+        // basePath defaults to `/`
+        basePath: `/sideproject`,
+        // projectsPath defaults to `content/projects`
+        projectsPath: `content/cool-projects`
+      }
+    }
+  ]
+};
+```
+
+## 🌟 Supporting me
+
+Thanks for using this project! I'm always interested in seeing what people do with my projects, so don't hesitate to tag me on [Twitter](https://twitter.com/lekoarts_de) and share the project with me.
+
+Please star this project, share it on Social Media or consider supporting me on [Patreon](https://www.patreon.com/lekoarts)!
+
+If you want to hire me for **contract/freelance work**, you can do so! [Get in touch with me!](https://www.lekoarts.de/en/contact)

themes/gatsby-theme-emma-core/gatsby-config.js

@@ -0,0 +1,66 @@
+const withDefaults = require(`./utils/default-options`)
+
+module.exports = themeOptions => {
+  const options = withDefaults(themeOptions)
+  const { mdx = true } = themeOptions
+
+  return {
+    siteMetadata: {
+      siteTitle: `Emma`,
+      siteTitleAlt: `Emma - @lekoarts/gatsby-theme-emma`,
+      siteHeadline: `Emma - Gatsby Theme from @lekoarts`,
+      siteUrl: `https://emma.lekoarts.de`,
+      siteDescription: `Minimalistic portfolio with full-width grid, page transitions, support for additional MDX pages, and a focus on large images`,
+      siteLanguage: `en`,
+      siteImage: `/banner.jpg`,
+      author: `@lekoarts_de`,
+      basePath: options.basePath,
+      projectsPath: options.projectsPath,
+      pagesPath: options.pagesPath,
+    },
+    plugins: [
+      {
+        resolve: `gatsby-source-filesystem`,
+        options: {
+          name: options.projectsPath,
+          path: options.projectsPath,
+        },
+      },
+      {
+        resolve: `gatsby-source-filesystem`,
+        options: {
+          name: options.pagesPath,
+          path: options.pagesPath,
+        },
+      },
+      mdx && {
+        resolve: `gatsby-plugin-mdx`,
+        options: {
+          gatsbyRemarkPlugins: [
+            {
+              resolve: `gatsby-remark-images`,
+              options: {
+                maxWidth: 820,
+                quality: 90,
+                linkImagesToOriginal: false,
+              },
+            },
+          ],
+          plugins: [
+            {
+              resolve: `gatsby-remark-images`,
+              options: {
+                maxWidth: 820,
+                quality: 90,
+                linkImagesToOriginal: false,
+              },
+            },
+          ],
+        },
+      },
+      `gatsby-transformer-sharp`,
+      `gatsby-plugin-sharp`,
+      `gatsby-plugin-typescript`,
+    ].filter(Boolean),
+  }
+}