Feature Request: 'unmount' prop to control whether the menu should unmount when closed

[rkalis]

As it is right now, the menu mounts when menuIsOpen and unmounts when !menuIsOpen. There are cases for which it would be preferable that the menu is always mounted, but is hidden with display: none when !menuIsOpen. For example, Headless UI offers an unmount prop in their Dropdown Menu component: https://headlessui.com/react/menu#menu-items