Host the web app in Github pages

[joanroig]

Add a Github page with the web app deployed to make it available from everywhere.
If possible, auto-build the master branch in a Github action and deploy it automatically, see #12
Depends on #44.

[joanroig]

The websocket server needs to use secure connection, error on Chrome after deployment: The page was loaded over HTTPS, but attempted to connect to the insecure WebSocket endpoint 'ws://.../?