Add "1 Finger Double Tap and Move" trigger support

It would be awesome to have a trigger for double tap and move.

Here's the sequence of actions to trigger it:

  1. Tap trackpad once (tap down + tap up)
  2. Put finger on trackpad again (tap down)
  3. Start moving finger without lifting it on a second tap.

As you move finger up/down (or left/right) on a second tap, some action may called continuously, for example zoom a page in/out, or scroll a page.

Reference: On phones, many apps support one-finger zooming using such a gesture.