Add attribute system with core stats and gameplay components

GameCore/ECS/Interfaces/ISystem.cs

@@ -0,0 +1,17 @@
+namespace GameCore.ECS.Interfaces;
+
+/// <summary>
+/// The contract for all game logic systems.
+/// Systems are stateless classes that contain all the logic.
+/// They operate on entities that possess a specific set of components.
+/// For example, a MovementSystem would operate on entities with PositionComponent and VelocityComponent.
+/// </summary>
+public interface ISystem
+{
+    /// <summary>
+    /// The main update method for a system, called once per game loop.
+    /// </summary>
+    /// <param name="world">A reference to the main World object to query for entities and components.</param>
+    /// <param name="deltaTime">The time elapsed since the last frame.</param>
+    void Update(World world, float deltaTime);
+}