Make it easier to overcome the magnetic force when grabbing at a magnetic mark and dragging away

[loucadufault]

Note that clicking right next to the magnetic mark should not trigger this effect, only dragging away from the magnetic mark should.

So long as we can get the previous value in the onChange hook (as well as the newValue), then we can check if the previous value was both 1) closer to a magnetic mark than the newValue (but not on the magnetic mark) and 2) in the (potentially scaled) radius of that magnetic mark. Then we would know that we were escaping that magnetic mark, and to continue escaping it.