add fps limit on window at construction

sources/System/Renderer/RenderScreenSystem.cpp

@@ -15,10 +15,13 @@ namespace BBM
 		}),
 		_window(window),
 		_camera(Vector3f(), Vector3f(), Vector3f(0, 1, 0), 50, CAMERA_PERSPECTIVE)
-	{}
+	{
+		this->_window.setFPS(RenderScreenSystem::FPS);
+	}
 
 	void RenderScreenSystem::onSelfUpdate()
 	{
+		this->_window.drawFPS(RAY::Vector2(1, 1));
 		this->_window.draw();
 		this->_window.clear();
 		this->_window.useCamera(this->_camera);

sources/System/Renderer/RenderScreenSystem.hpp

@@ -17,6 +17,9 @@ namespace BBM
 
 		//! @brief The camera used to render.
 		RAY::Camera::Camera3D _camera;
+
+		//! @brief Window framerate limit
+		static constexpr short FPS = 30;
 	public:
 		//! @brief A method called after all entities that this system manage has been updated.
 		//! @note render on screen here