add native promise support

[cking]

[Tapppi]

Planned for sure, but think I will try to get this in with a new rewrite with PR's to merge into sindresorhus/exit-hook. I'll make sure to release promise support in this library as well even if that PR goes through.

[cking]

that would be highly appreciated.

[Parcley]

any news on native promises?

[tcd]

So that's a no on the news?