Add Capture variants

[mDibyo]

React has two versions of every event: onClick and onClickCapture where the capture version runs in the capture phase. It would be nice to have equivalents for pointer events as well.

[MilllerTime]

Thanks for bringing this up @mDibyo! This is certainly an omission, and slipped my mind as I can't recall the last time I've ever personally needed the capture phase of any event. Good looks 😄

Only one thing worries me about adding onPointer*Capture alternatives: PEP doesn't support the capture phase, meaning it will still be unavailable in Safari even if <Pointable> accepts it. This comment mentions that PEP only supports target and bubbling phases. It was then explained in this later comment that polyfilling the capture phase isn't a priority since jQuery and Polymer never did it, with nearly nonexistent developer pushback. So, it doesn't look like that is going anywhere.

I definitely don't want a silent failure, so I could feature detect pointer events and log a nice dev warning about using the polyfill including mention of the lack of capture support. Of course that doesn't fix the real problem.

Do you have a use case for this? Would lack of Safari support be an issue?