Add a Nginx reverse proxy to combine all the used ports into one single port

This will allow this web UI to sit nicely behind a reverse proxy.

Dynamically set the ports used for the
- VNC service
- noVNC service
- Pulseaudio socket
- VNC audio transport websocket

Remove all mentions of the above used ports in the Dockerfile.

overlay/etc/supervisor.d/steam.ini

@@ -6,7 +6,7 @@ autorestart=true
 # Retry a restart a few times.
 #   This allows this container to start up before X is ready and restart the process until it becomes available.
 #   Each restart will have a small delay of a few seconds. So 50 attempts should be a few mins.
-startretries=50 
+startretries=50
 priority=50
 user=%(ENV_USER)s
 directory=/home/%(ENV_USER)s