In case this helps anyone: the syntax module requires `window.hljs`, and something like
```js
import hljs from 'highlight.js';
window.hljs = hljs;
import Quill from 'quill';
```
doesn't work because `import`s are asynchronous and happen before the script (and hence the `window.hljs` line) is even executed. However, if we use synchronous `require` then there's no problem:
```js
window.hljs = require('highlight.js');
const Quill = require('quill');
```
(Of course, using hljs with a bundler is still a pain since AFAIK we have to manually register all the languages we might need, or get a ~1MB bundle with all languages...)