cursor for grab/drag

[eyaler]

in chess.com for example you have the 'grab' cursor when hovering your pieces and 'grabbing' cursor while grabbing. would be nice to have this as a default or easy option.

otherwise you can do:

.dragging-4a6c1 {
    cursor: grabbing;
}

function onMouseenterSquare(evt, domEvt) {
    if (evt.piece?.startsWith(playerColorLetter))
        myBoard.style.cursor = 'grab'
}

function onMouseleaveSquare(evt, domEvt) {
    myBoard.style.cursor = 'auto'
}

as well as myBoard.style.cursor = 'auto' for the onDrop snapback

additional logic is needed to take into account whether it's the player's turn.