Add flag useDragToDismiss to enable/disable drag to dismiss gesture

[adrianolc]

In my app, we have a screen that we want only to allow the zoom feature and not have the drag to dismiss action.

One way I found to control it is adding the flag useDragToDismiss similar to the useFlingToDismissGesture where we can control at the library init and verify if it's on in the onGestureListener.onScroll callback right before call`processDrag.

[igreenwood]

Good 😄