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.

docs/unraid.md

@@ -45,13 +45,10 @@ Unraid's Linux kernel by default does not have the modules required to support c
 
     > __Warning__
     >
-    > Be aware that, by default, this container requires at least 8083, 5900, 5901, 32123, and 2222 available for the WebUI, VNC, Web Audio, and SSH to work. It will also require any ports that Steam requires for Steam Remote Play.
+    > Be aware that, by default, this container requires at least 8083 and 2222 available for the WebUI and SSH to work. It will also require any ports that Steam requires for Steam Remote Play.
 
     You can override the default ports used by the container with these variables:
     - PORT_SSH (Default: 2222)
-    - PORT_VNC (Default: 5900)
-    - PORT_AUDIO_STREAM (Default: 5901)
     - PORT_NOVNC_WEB (Default: 8083)
-    - PORT_AUDIO_WEBSOCKET (Default: 32123)
 
 3. No server restart is required, however. Ensure that the **steam-headless** Docker container is recreated after installing the **uinput** plugin for it to be able to detect the newly added module.