Snap points are not apparent while dragging

The handle currently snaps to a valid snap point at the end of a drag. While the handle is dragged, the control calls onValuesUpdated with all of the values between the snap points.

This behavior is a little odd because it's a little ambiguous what a valid snap point is until you stop dragging the handle. Snap points can be defined arbitrarily and it's weird to allow the UI to get updated (through onValuesUpdated) with any value that is not a valid snap point.

It would be beneficial if the snap points were reflected while the user was dragging the handle and not just after letting go.

FYI @ljharb