Add option to automatically start the plugin on a given scene

This functionality was lost with the removal of the "Scene trigger" tab.

lib/advanced-scene-switcher.cpp

@@ -538,6 +538,7 @@ static void handleSceneChange()
 	}
 
 	switcher->checkDefaultSceneTransitions();
+	switcher->CheckAutoStart();
 }
 
 static void setLiveTime()