selectPiece method
Moves pieceId using the current roll, animating it one cell at a
time. Completes once the move is committed.
Throws a StateError if it is a bot's turn or no roll is pending,
and an ArgumentError if pieceId is not a legal move. Calls made
while another move is animating are ignored.
Implementation
Future<void> selectPiece(int pieceId) async {
_checkHumanTurn('selectPiece');
await _select(pieceId);
}