Revert "js: Update shims setup"

This reverts commit 704987dc1c.

content/en/hugo-pipes/js.md

@@ -152,11 +152,10 @@ It's a common practice to load external libraries using a content delivery netwo
 First, add React and ReactDOM [CDN script tags](https://reactjs.org/docs/add-react-to-a-website.html#tip-minify-javascript-for-production) in your HTML template files. Then create `assets/js/shims/react.js` and `assets/js/shims/react-dom.js` with the following contents:
 ```js
 // In assets/js/shims/react.js
-export let React = window.React;
+module.exports = window.React;
 
 // In assets/js/shims/react-dom.js
-export let ReactDom = window.ReactDom;
-
+module.exports = window.ReactDOM;
 ```
 
 Finally, add the following to your project's `package.json`: