Missleading keyboard behaviour in emoji picker

[mejo-]

Describe the bug There's room for improvement in the keyboard navigation in emoji picker:

• [ ] When emoji picker is open, Esc should only close emoji picker, not the full editor modal
• [ ] Tab should insert the selected emoji
• [ ] When emoji picker is open, Esc followed by Return inserts the last selected emoji. This should not happen. It's only reproducible in public shares or Collectives right now, due to the fact that Esc closes the whole editor modal in other cases.