Allow keyboard input for puzzles

Currently, the UI only allows keyboard input when playing games.

It would be nice to allow the same feature in puzzles so people can get used to the coordinates in a less stressful setting (real game or coordinate training).

I agree.

I agree, it's an issue but nobody has volunteered to fix and test it yet (I have tried; it's not easy):
github.com/ornicar/lila/issues/5724