Add item spawn menu

Fix game over bug
Start adding more implementation for jewels

Zennysoft.Game.Ma/src/Components/ExperiencePointsComponent.cs

@@ -51,6 +51,7 @@ public class ExperiencePointsComponent : IExperiencePointsComponent
     var cappedAmount = Math.Min(baseExpGain + _currentExp.Value, _expToNextLevel.Value);
     _currentExp.OnNext(cappedAmount);
   }
+  public void ModifyExpGainRate(double newRate) => _expGainRate.OnNext(newRate);
 
   public void LevelUp()
   {