Popover: support item with active state

[asaf]

Hey,

Some notes to make a menu such as the Branded Menu to function:

• Popover.Item with {({ active }) => (...) like the Menu.Item
• Up / Down should change the active item.
• An event that responds to mouse click / enter key on the active item.

Thanks.

[asaf]

Sorry, this is a dup of discussion 296, you can close one of those. thanks!