Update README

[gtokman]

Great library!

Would be awesome to update the REAME with new examples as the offset and gesture mode are req.

SnapDraggingModifier(
     gestureMode: .normal,
      offset: $offset                             
 ))

Also, would be great to get an example on how to snap to corners (top, bottom, left, right, middle) just like FaceTime. I could see that a common use case for folks using this library.