Mouse event for auxclick

[joe-op]

The auxclick ui event (w3 / mdn) isn't included as a MouseEvent. This is what Chrome and Firefox fire for middle clicks.

I had to work around this recently to get a Halogen a component to handle middle clicks. If I understand correctly, auxclick would need to be here in MouseEvent , in purescript-indexed-dom's MouseEvents, and in Halogen.HTML.Events for it to integrate the same way onClick does. I can make PRs for those changes if that's correct (and if auxclick fits here).

[JordanMartinez]

That sounds right. Go ahead and open up PRs for those.