Add attempt for Entity::GetComponent

include/entity.h

@@ -8,12 +8,9 @@ class Entity {
 public:
   template <typename CompT, typename... Args>
   Component *AddComponent(Args &&...args);
+  template <typename CompT> Component *GetComponent();
 
-  void Init();
-  void Draw();
   void Update();
-  void FixedUpdate();
-  void Destroy();
 
 private:
   std::vector<std::unique_ptr<Component>> components;