Add support for running a container using only a XvFB framebuffer for the X server

As requested by a user, this gives the option to run a headless steam for the purpose of downloading games and not for playing them.

overlay/etc/cont-init.d/90-configure_xorg.sh

@@ -63,8 +63,10 @@ function configure_x_server {
         sed -i 's|^autostart.*=.*$|autostart=true|' /etc/supervisor.d/xorg.ini
     elif [ "${MODE}" == "fb" ] | [ "${MODE}" == "framebuffer" ]; then
         echo "Configure container to use a virtual framebuffer as the X server"
-        # Disable supervisord script
+        # Disable xorg supervisord script
         sed -i 's|^autostart.*=.*$|autostart=false|' /etc/supervisor.d/xorg.ini
+        # Enable xvfb supervisord script
+        sed -i 's|^autostart.*=.*$|autostart=true|' /etc/supervisor.d/xvfb.ini
     fi
     # Make startup script executable
     chmod +x /usr/bin/start-xorg.sh

overlay/etc/supervisor.d/xvfb.ini

@@ -0,0 +1,13 @@
+
+[program:xvfb]
+autostart=false
+autorestart=true
+priority=20
+user=root
+command=/usr/bin/Xvfb %(ENV_DISPLAY)s -screen 0 "%(ENV_DISPLAY_SIZEW)sx%(ENV_DISPLAY_SIZEH)sx24"
+environment=DISPLAY="%(ENV_DISPLAY)s"
+stopsignal=QUIT
+stdout_logfile_maxbytes=10MB
+stdout_logfile_backups=7
+stderr_logfile_maxbytes=10MB
+stderr_logfile_backups=7