Add attribute system with core stats and gameplay components

GameCore/Events/EntityDiedEvent.cs

@@ -0,0 +1,9 @@
+using GameCore.ECS;
+using GameCore.Events.Interfaces;
+
+namespace GameCore.Events;
+
+public readonly struct EntityDiedEvent(Entity entity) : IEvent
+{
+    public readonly Entity Entity = entity;
+}