Update CRA guide

Create React App is the most looked at resource by users here on GitHub.
But it’s suggesting an old, unmaintained, and buggy way to use MDX.

This instead updates the guide to use our maintained projects, without
having to eject from CRA.

As CRA itself is an ever-changing “init” tool, which can support MDX by
following a couple steps, I don’t think it’s wise to have an example in
the project: we want folks to do `npx create-react-app ...`, not clone
our custom example.

Not having CRA checked in also makes for a faster `yarn install`.

Perhaps developing our own [CRA
template](https://create-react-app.dev/docs/custom-templates) might be
nice for the future, but for now I’ve kept it at an up to date and
working guide.

Related to GH-1015.
Related to GH-1388.

Closes GH-365.
Closes GH-589.

Author: wooorm

.gitignore

@@ -11,7 +11,6 @@ bundle.js
 tmp
 artifacts
 .*cache
-public
 .npmrc
 .nyc_output/
 coverage/

docs/getting-started/create-react-app.mdx

@@ -1,50 +1,92 @@
 # Create React App
 
-Please note there’s a [known bug][] with
-the macro so live reloading doesn’t
-currently work.
-
-With Create React App you will need to use
-[`mdx.macro`][mdx-macro].
+First, create a new app with [CRA][] and change directory to enter it:
 
 ```sh
 npx create-react-app my-app
-yarn add mdx.macro
+cd my-app
+```
+
+Second, we need to configure some build tools.
+Install [`@mdx-js/loader`][loader] and [`babel-loader`][babel-loader] as dev
+dependencies:
+
+```sh
+yarn add @mdx-js/loader babel-loader --dev
+```
+
+Also make sure that JSX in MDX is handled by Babel by creating a `.babelrc` JSON
+file in the project root of `my-app`:
+
+```json
+{
+  "presets": ["@babel/preset-react"]
+}
+```
+
+Third, we can add our MDX content.
+Create an MDX file `Content.mdx` in the `src/` folder:
+
+```mdx
+export const Box = () => (
+  <div style={{padding: 20, backgroundColor: 'tomato'}} />
+)
+
+# Hello, world!
+
+This is **markdown** with <span style={{color: "red"}}>JSX</span>: MDX!
+
+<Box />
 ```
 
-Then create the following `src/App.js`:
+And to use that MDX content in the app, replace the contents of `App.js` in the
+`src/` folder with:
 
 ```js
-// src/App.js
-
-import React, {lazy, Component, Suspense} from 'react'
-import {importMDX} from 'mdx.macro'
-
-const Content = lazy(() => importMDX('./Content.mdx'))
-
-class App extends Component {
-  render() {
-    return (
-      <div>
-        <Suspense fallback={<div>Loading...</div>}>
-          <Content />
-        </Suspense>
-      </div>
-    )
-  }
+/* eslint-disable import/no-webpack-loader-syntax */
+import Content from '!babel-loader!@mdx-js/loader!./Content.mdx'
+
+function App() {
+  return <Content />
 }
 
 export default App
 ```
 
-And then create the following `src/Content.mdx`:
+We’re almost done!
+To start the development server, run:
 
-```md
-# Hello, world!
+```sh
+yarn start
 ```
 
-[See the full example][cra-example]
+**…but you will probably get this error**:
+
+```txt
+$ react-scripts start
+
+There might be a problem with the project dependency tree.
+It is likely not a bug in Create React App, but something you need to fix locally.
+
+The react-scripts package provided by Create React App requires a dependency:
+
+  "babel-loader": "$VERSION"
+…
+```
+
+CRA expects a certain `babel-loader` version but MDX also needs one.
+To fix the error, make sure the two `babel-loader` versions match, by running
+the following:
+
+```sh
+yarn add babel-loader@$VERSION --dev
+```
+
+(where `$VERSION` is the version number printed in the error message, such as
+`8.1.0`).
+
+Then, running `yarn start` again should do the trick! ✨
 
-[mdx-macro]: https://www.npmjs.com/package/mdx.macro
-[cra-example]: https://github.com/mdx-js/mdx/tree/master/examples/create-react-app
-[known bug]: https://github.com/facebook/create-react-app/issues/5580
+[cra]: https://github.com/facebook/create-react-app
+[loader]: https://github.com/mdx-js/mdx/tree/main/packages/loader
+[babel-loader]: https://webpack.js.org/loaders/babel-loader/

docs/getting-started/index.mdx

@@ -411,7 +411,6 @@ playing around you can use `npm init`:
 - `npm init mdx` [`webpack`](/getting-started/webpack)
 - `npm init mdx` [`parcel`](/getting-started/parcel)
 - `npm init mdx` [`next`](/getting-started/next)
-- `npm init mdx` [`create-react-app`](/getting-started/create-react-app)
 - `npm init mdx` [`gatsby`](/getting-started/gatsby)
 - `npm init mdx` [`react-static`](/getting-started/react-static)
 

examples/create-react-app/.babelrc

@@ -1,52 +1,6 @@
 # Create React App
 
-This project was bootstrapped with [Create React App](https://github.com/facebook/create-react-app).
+<!-- To do: link to website when it’s fixed. -->
 
-## Available Scripts
-
-In the project directory, you can run:
-
-### `npm start`
-
-Runs the app in the development mode.<br />
-Open [http://localhost:3000](http://localhost:3000) to view it in the browser.
-
-The page will reload if you make edits.<br />
-You will also see any lint errors in the console.
-
-### `npm test`
-
-Launches the test runner in the interactive watch mode.<br />
-See the section about [running tests](https://facebook.github.io/create-react-app/docs/running-tests) for more information.
-
-### `npm run build`
-
-Builds the app for production to the `build` folder.<br />
-It correctly bundles React in production mode and optimizes the build for the best performance.
-
-The build is minified and the filenames include the hashes.<br />
-Your app is ready to be deployed!
-
-See the section about [deployment](https://facebook.github.io/create-react-app/docs/deployment) for more information.
-
-### `npm run eject`
-
-**Note: this is a one-way operation.
-Once you `eject`, you can’t go back!**
-
-If you aren’t satisfied with the build tool and configuration choices, you can `eject` at any time.
-This command will remove the single build dependency from your project.
-
-Instead, it will copy all the configuration files and the transitive dependencies (Webpack, Babel, ESLint, etc) right into your project so you have full control over them.
-All of the commands except `eject` will still work, but they will point to the copied scripts so you can tweak them.
-At this point you’re on your own.
-
-You don’t have to ever use `eject`.
-The curated feature set is suitable for small and middle deployments, and you shouldn’t feel obligated to use this feature.
-However we understand that this tool wouldn’t be useful if you couldn’t customize it when you are ready for it.
-
-## Learn More
-
-You can learn more in the [Create React App documentation](https://facebook.github.io/create-react-app/docs/getting-started).
-
-To learn React, check out the [React documentation](https://reactjs.org/).
+[See this guide](https://github.com/mdx-js/mdx/blob/main/docs/getting-started/create-react-app.mdx)
+for how to use MDX with CRA!