JSDOM gotchas (ref: `jsdom v16.1.0`)

jsdom-gotchas.md

1. fetch() is unsupported.

2. XMLHttpRequest does not pass through JSOM.ResourceLoader. (jsdom/jsdom#1393)

3. Does not respect synchronous execution of <script> tags. For eg.

<script src="run-first.js"></script>
<script src="run-second.js"></script>
<!-- You will expect `run-first.js` to be downloaded **and** run, 
     before `run-second.js` is. AFAICT `jsdom` runs both asynchronously. -->