Add support for runnin a secondary instance of steam

This requires that you still have setup a primary container instance of this image.
We can then run a secondary instance of steam that will use the existing X server.

We are still limited to running one of these steam instances at a time.

overlay/etc/supervisor.d/steam.ini

@@ -6,7 +6,8 @@ autorestart=true
 priority=50
 user=%(ENV_USER)s
 directory=/home/%(ENV_USER)s
-command=/usr/game/steam -bigpicture
+# command=/usr/games/steam -bigpicture
+command=/usr/games/steam
 environment=HOME="/home/%(ENV_USER)s",USER="%(ENV_USER)s",DISPLAY="%(ENV_DISPLAY)s"
 stopsignal=QUIT
 stdout_logfile=/home/%(ENV_USER)s/.cache/log/steam.log