vomnibar: goPage: better checks
vomnibar: goPage: better checks

* use completions.total to limit pagedown
* always allow pageup
* do nothing if both event.deltaX and .deltaY are `0`/`-0`
  * e.g. : use touch pad to scroll right

gdh1995/vimium-plus,gdh1995/vimium-plus,gdh1995/vimium-plus