[Request] autocomplete users

[xylolink]

Is your feature request related to a problem? Please describe.
need autocompletion of mentionned users when starting a new post

Describe the solution you'd like
Typing "@" automatically suggest accounts from followers/following list
Typing any other caracters filters the account list with these caracters

Describe alternatives you've considered
None

Additional context
None

[alicerunsonfedora]

We can definitely take a look at implementing something like this in a future feature update after v1.1.0.