Fix tap-to-show call controls on iOS

[fkwp]

iOS Safari doesn't reliably fire click on plain <div>s, so we listen for pointerup instead. Scrolls end in pointercancel, not pointerup, so this still only fires for taps.

[robintown]

This generally sounds fine as a fix. I will just test in a couple different browsers and layouts before approving.

We used to use a touchend rather than click handler for this, and that relied on a timer to determine whether the input was actually a tap rather than a long press. Now that I'm thinking about it again, I don't know why we should care that much about the press length. It might still make sense to listen for touchend rather than pointerup, for simplicity's sake, but also not a big deal.

Oops, I meant to simply comment

[toger5]

This is for a follow up discussion/PR:
We might also want to hide the controls on web if the window is very small:

In this case the PointerUp event is helpful as it also allows to show/hide the controls on web.

For the same reason I approve merging with pointUp instead of touchEnd.