Introduce ServiceWorker to intercept normal HTTP req/res

[whitphx]

Apart the WebSocket communication, Streamlit also uses many HTTP endpoints for various purposes including serving media files and custom component resources.
To make use of these existing HTTP endpoints and the corresponding client implementations with a minimum amount of changes, it looks like ServiceWorker is a good way, compared to re-implementing these communications on top of WebWorker messaging.

Considerations

• ServiceWorker works in a "progressive" manner, so its full functionality may not be available at the initial time before downloading completes.
• ServiceWorker may fail to be installed if the script origin is different from the page origin: Is it possible to serve service workers from CDN/remote origin? w3c/ServiceWorker#940

[whitphx]

As stated in the second point of the considerations above, ServiceWorker won't work when served from remote origin.
In the case of CRA, it fails into this code block and leads to no effect:

stlite/packages/playground/src/serviceWorkerRegistration.ts

Lines 30 to 35 in 91ba9a0

	if (publicUrl.origin !== window.location.origin) {
	// Our service worker won't work if PUBLIC_URL is on a different origin
	// from what our page is served on. This might happen if a CDN is used to
	// serve assets; see https://github.com/facebook/create-react-app/issues/2374
	return;
	}