Add attribute system with core stats and gameplay components

GameCore/Combat/Effects/DamageEffect.cs

@@ -0,0 +1,15 @@
+using GameCore.Combat.Interfaces;
+using GameCore.Events;
+
+namespace GameCore.Combat.Effects;
+
+public class DamageEffect(float amount) : IEffect
+{
+    public void Execute(EffectContext context)
+    {
+        if (context.Target == null)
+            return;
+
+        context.World.PublishEvent(new DamageDealtEvent(context.Target.Value, amount));
+    }
+}