In study , add option to not auto move to next line

[DovAmir]

After solving a line in the study, it automatically moves to the next line.
Allow to not auto move to next line, because player might want to reflect on the line he just solved, analyze it in lichess, play against stockfish etc...
Board reset delay does not help.

[blnwe]

Yes, I think adding a way to disable board reset would be great !