Serve web client over HTTPS that automatically connects to a proxy instance

[pierd]

So that a proxied server can be reached from the browser. This would make super easy to show the game hosted locally to others - just start your local server and send provided URL to others for them to join via browser.

This will require:

• using HTTPS for serving web content
• handling webtransport connections
• serving a mostly static website for each proxy instance (similar to what Ambient already does: Make it easier to self host Ambient servers Ambient#1153