Sort rooms based on their API position

osu.Game/Screens/Multi/IRoomManager.cs

@@ -10,6 +10,11 @@ namespace osu.Game.Screens.Multi
 {
     public interface IRoomManager
     {
+        /// <summary>
+        /// Invoked when the <see cref="Room"/>s have been updated.
+        /// </summary>
+        event Action RoomsUpdated;
+
         /// <summary>
         /// All the active <see cref="Room"/>s.
         /// </summary>