Add attribute system with core stats and gameplay components

GameCore/Combat/DeathComponent.cs

@@ -0,0 +1,13 @@
+using GameCore.ECS.Interfaces;
+
+namespace GameCore.Combat;
+
+/// <summary>
+///     A simple "marker" component. When the DamageSystem determines an entity's
+///     health has dropped to 0 or below, it adds this component to the entity.
+///     Other systems (or the presenter layer) can then react to this, for example,
+///     by playing a death animation, creating a ragdoll, and eventually destroying the entity.
+/// </summary>
+public class DeathComponent : IComponent
+{
+}