Compatability between inject and CJS

So, the [docs](https://esbuild.github.io/) are kind of a weird mishmash of `cjs` and `esm`, although they mention **CommonJS** as a "major feature".

We've hit a snag with trying to `inject` some global libraries (like **jQuery**, **React** and the like) into our bundle. Let's say we have a file called `vendor`, which pass to `inject`, containing the following:

```javascript
module.exports = {
$: require('jquery'),
React: require('react'),
ReactDOM: require('react-dom')
};
```
^ The above won't work, and the bundle will complain about a missing **React** dependency. However, transforming the file to `esm` -format will work:

```javascript
import * as $ from 'jquery';
import * as React from 'react';
import * as ReactDOM from 'react-dom';

export { $, React, ReactDOM }
```
Am I to understand that `cjs` simply won't work with `inject`? If so, are there other features that behave similarly? The docs don't really make this clear.

Start with the inject documentation at https://esbuild.github.io/ and reproduce the CommonJS and ESM examples using jQuery, React, and ReactDOM. Clarify whether CommonJS works with inject and identify any other features with similar module-format behavior; done when the documentation states these limitations clearly.

Written by the indexing model from the issue text.