Add WebWorker Support

Created by: dansiviter

Add ability to load WebWorkers (and SharedWorkers?) via the react-scripts. My use-case is for using latency (and debug) sensitive protocols over WebSocket which may get dumped by the server if no activity occurs.

There has been a lot of discussion regarding this on #1277 (closed) but no definitive answer and now closed. Also, I'm a server-side dev so JavaScript PR is not my forte, and neither is ejecting the scripts as that looks scary.