add export message box

src/app_layout.cpp

@@ -27,7 +27,9 @@ void App::init_toolbar_main()
         button->on_click = [this, button](Node*) {
             if (canvas)
             {
-                canvas->m_canvas->export_equirectangular(data_path);
+                canvas->m_canvas->export_equirectangular(data_path, [this]{
+                    message_box("Export", "blabl");
+                });
             }
         };
     }