Add stackable items

Zennysoft.Game.Ma/src/items/throwable/ThrowableItem.cs

@@ -2,12 +2,13 @@ using Chickensoft.AutoInject;
 using Chickensoft.Introspection;
 using Chickensoft.Serialization;
 using Godot;
+using Zennysoft.Game.Abstractions;
 using Zennysoft.Ma.Adapter;
 
 namespace Zennysoft.Game.Ma;
 
 [Meta(typeof(IAutoNode)), Id("throwable_item")]
-public partial class ThrowableItem : InventoryItem
+public partial class ThrowableItem : InventoryItem, IStackable
 {
   public override void _Notification(int what) => this.Notify(what);
 
@@ -40,10 +41,14 @@ public partial class ThrowableItem : InventoryItem
 
   public void SetDescription(string description) => Stats.Description = description;
 
-  public int Count { get; }
+  [Save("throwable_item_count")]
+  public int Count { get; private set; } = 1;
 
   [Export]
   [Save("throwable_item_stats")]
   public ThrowableItemStats Stats { get; set; }
+
   public override Texture2D GetTexture() => Stats.Texture;
+
+  public void SetCount(int count) => Count = count;
 }