new feature: nonDraggableIndices

[Bader-Al]

nonDraggableIndices can be used along with lockedIndices for certain use-cases.

[karvulf]

Hello @Bader-Al
Thank you for opening the PR. I think there might be an issue where you call:

!widget.nonDraggableIndices.contains(key.value);

You define in a list the indices that should not be draggable. But there you say that it depends on the value of the key that is not the index. Instead you need to add a key variable that you increase in the for-loop. Or you change the for loop to the classical one.