Add settings icon, close window when pressing the close button

include/gui/CheckBox.hpp

@@ -16,6 +16,8 @@ namespace gsr {
         void draw(mgl::Window &window, mgl::vec2f offset) override;
 
         mgl::vec2f get_size() override;
+
+        void set_checked(bool checked);
         bool is_checked() const;
     private:
         mgl::vec2f get_checkbox_size();