fix: menu docs

docs/usage/guides/visual/menu.md

@@ -29,7 +29,7 @@ Create a `Menu` instance:
 // here `"quit".to_string()` defines the menu item id, and the second parameter is the menu item label.
 let quit = CustomMenuItem::new("quit".to_string(), "Quit");
 let close = CustomMenuItem::new("close".to_string(), "Close");
-let submenu = Menu::new().add_item(quit).add_item(close);
+let submenu = Submenu::new("File", Menu::new().add_item(quit).add_item(close));
 let menu = Menu::new()
   .add_native_item(MenuItem::Copy)
   .add_item(CustomMenuItem::new("hide", "Hide"))