Registers a submenu. This makes it accessible for navigation, and sets its parent menu to this menu.

Optionally, you can specify the identifier of a different parent menu as a second argument. The parent menu is the menu that is targeted when backwards navigation is performed.

Note that once you registered a submenu, it is sufficient to call bot.use(menu) for the parent menu only. You do not need to make all submenus interactive by passing them to bot.use.