improve onChange example
improve onChange example

ThiagoGarciaAlves/chessboardjs,blipjoy/chessboardjs,blipjoy/chessboardjs,mattyhead/chessboardjs,mattyhead/chessboardjs,ngocdaothanh/chessboardjs,raneku/chessboardjs,blipjoy/chessboardjs,oakmac/chessboardjs,mauronunez/chessboardjs,mauronunez/chessboardjs,ThiagoGarciaAlves/chessboardjs,raneku/chessboardjs,raneku/chessboardjs,ngocdaothanh/chessboardjs