Tab to Autocomplete

Right now you have to type enter in order to trigger (insert) an auto-completion. It would be nice if typing tab also triggered (inserted) the auto-completion. A lot of text editors use tab and it would be nice if Postico mimicked this behavior.

Currently typing tab while this auto-complete overlay is open takes you to the top of the list.

Start at the autocomplete overlay and locate the existing Enter key handling, then inspect how Tab currently moves to the top of the list. Done means pressing Tab while the overlay is open inserts the selected autocomplete result instead of moving through the list, while Enter continues to work.

Written by the indexing model from the issue text.