Run Sunshine as a service

Goodbye Flatpak Sunshine. Hello AppImage.
Until a deb package is available for Debian Bookworm, we can just run sunshine as an AppImage.
It is faster to startup and is a little less bloated.

The goal here is to run Sunshine as a service managed by supervisord so that it is kept running and is restarted automatically if stopped.

overlay/templates/sunshine/sunshine.conf

@@ -28,6 +28,10 @@
 #
 min_log_level = info
 
+# A list of commands to be run before/after all applications.
+#   If any of the prep-commands fail, starting the application is aborted.
+global_prep_cmd = [{"do":"/usr/bin/xfce4-minimise-all-windows","undo":"/usr/bin/sunshine-stop"}]
+
 # The origin of the remote endpoint address that is not denied for HTTP method /pin
 # Could be any of the following values:
 #   pc|lan|wan
@@ -95,7 +99,7 @@ min_log_level = info
 # ping_timeout = 10000
 
 # The file where configuration for the different applications that Sunshine can run during a stream
-file_apps = /home/default/sunshine/apps.json
+file_apps = apps.json
 
 # Percentage of error correcting packets per data packet in each video frame
 # Higher values can correct for more network packet loss, but at the cost of increasing bandwidth usage
@@ -111,7 +115,7 @@ file_apps = /home/default/sunshine/apps.json
 #
 # Unlike simply broadcasting to multiple Client, this will generate distinct video streams.
 # Note, CPU usage increases for each distinct video stream generated
-# channels = 1
+channels = 2
 
 # The back/select button on the controller
 # On the Shield, the home and powerbutton are not passed to Moonlight