[ADD] the pause menu can be accessed with the 'P' key. the real button are not implemented yet.

src/scenes/startup_Scene.h

@@ -12,6 +12,7 @@ namespace scene
 		scene::Scenes return_value = scene::Scenes::STARTUP;
 
 	public:
+		~Startup_Scene();
 		Scenes start(GLFWwindow* window) override;
 		void render() override;
 		void update(GLFWwindow* window) override;