Limit selected chips count ChipsChoice.multiple mode

[christxph]

Hi, first of all thanks a lot for this great library - saved us a lot of time already!

We were looking for a way to limit how many chips can be selected in ChipsChoice.multiple mode. If the limit is reached all other chips are disabled. We have already implemented this manually, but I think this would make a great addition to this library if it worked out of the box.

Edit: Here is how we are doing it at the moment (which is super simple anyways):

ChipsChoice.multiple(
  [...]
  choiceItems: C2Choice.listFrom(
    [...]
    disabled: (i, v) => !_selectedItems.contains(_allItems[i]) && _selectedItems.length >= _maxSelectedItems
  ),
)