arrow keys to navigate contextmenu

[Jacky0299]

No description provided.

[prushforth]

@Malvoz we have an a11y issue we need an expert opinion on: Can we neglect use of tab keys to navigate the context menu? Chrome context menu itself does not seem to respond to tab keys, but maybe we have got the "button" semantic in place so we need to maintain tab key support. WDYT?

[prushforth]

Small visual difference noted when you pull out the Copy > submenu, it puts a focus ring on the first item; generally the focus ring is only shown when using keyboard.

Unlike the hover behaviour, the focus ring doesn't move when you move your pointer, so I believe the focus ring should not be shown in this case (when using the pointer only):

[prushforth]

Awesome work Jacky 👍👏