- Ensure that the adder location is always below the highlighted selection on a touch devices so that it does not compete with the copy/paste bar.
- Add a little extra margin (10px) to the adder on touch devices to give room for the selection handles
- Add helper method `isTouchDevice` for touch devices
- Add comment in isSelectionBackwards to explain that iOS does not have the same selection object as non-iOS devices
- Add 1 missing test coverage case in adder.js