XP done

Assets/Game/Scripts/BuildingData.cs

@@ -41,6 +41,7 @@ public class BuildingLevel{
     public int level = 0;
     public List<BuildingStat> stats;
     public int price = 1000;
+    public int xpGain = 100;
     
     public BuildingLevel(int _level, List<BuildingStat> _stats, int _price){
         level = _level;