Keyboard Interactive Mention Suggestions

[i2h3]

Is your feature request related to a problem? Please describe.
I use my iPad with an external keyboard. When I start to type a mention, I get the usual list of suggestions. I cannot navigate or select the suggestions by keyboard, though. I have to tap on the screen. If I hit return while having an incomplete mention, that fragment is posted as a message.

Describe the solution you'd like
As natural in desktop environments, the list items should be focusable and navigable by arrow keys of external periphery. Hitting return should selected the highlighted suggestion. This would also increase accessibility.

Describe alternatives you've considered
Tapping on the screen is the default and only alternative and exactly what I want to avoid by using an external keyboard with physical keys. 😁

Additional context
None.