Implement inventory system with item management and pickup functionality

GameCore/Events/AddItemToInventoryEvent.cs

@@ -0,0 +1,11 @@
+using GameCore.ECS;
+using GameCore.Events.Interfaces;
+using GameCore.Inventory;
+
+namespace GameCore.Events;
+
+public readonly struct AddItemToInventoryEvent(Entity target, Item item) : IEvent
+{
+    public readonly Entity Target = target;
+    public readonly Item Item = item;
+}