Implement even more inventory/UI stuff

src/player/PlayerStatInfo.cs

@@ -45,6 +45,9 @@ namespace GameJamDungeon
     [Export]
     public int BonusDefense { get => _bonusDefense.Value; set => _bonusDefense.OnNext(value); }
 
+    [Export]
+    public double Luck { get => _luck.Value; set => _luck.OnNext(value); }
+
     // AutoProp backing data
     private readonly AutoProp<double> _currentHP = new AutoProp<double>(0);
     private readonly AutoProp<double> _maximumHP = new AutoProp<double>(0);
@@ -64,5 +67,7 @@ namespace GameJamDungeon
 
     private readonly AutoProp<int> _bonusAttack = new AutoProp<int>(0);
     private readonly AutoProp<int> _bonusDefense = new AutoProp<int>(0);
+
+    private readonly AutoProp<double> _luck = new AutoProp<double>(0.0);
   }
 }