emoji completion: Add a variation selector

This is a more keyboard-friendly version of variation
selector we have in the Emoji chooser.
4 jobs from wip/matthiasc/emoji-picker in 42 minutes and 7 seconds (queued for 2 minutes and 4 seconds)
Status Job ID Name Coverage
  Build
passed #24273
fedora-x86_64

25:56

passed #24274
win32
msys2-mingw32

03:45

 
  Flatpak
passed #24275
allowed to fail
flatpak:demo

05:20

passed #24276
allowed to fail
flatpak:widget-factory

12:05