fix TileBag code smell

Qwirkle/QwirkleClassLibrary/Games/Game.cs

@@ -21,7 +21,7 @@ namespace QwirkleClassLibrary.Games
     public class Game : IPlayer, IRules
     {
         [DataMember]
-        public TileBag? bag = null;
+        private TileBag? bag = null;
         
         [DataMember]
         public bool GameRunning { get; set; }