Feature: `usePromisify(..)` about tng-hooks

[getify]

I got stuck on #20 (mostly design choice wise) after getting quite a bit of work in on it. You can see that work in progress on this branch: https://github.com/getify/TNG-Hooks/tree/issue-20-externalize-context

But because of the nature of that change, it would invalidate any of these other features, so I wanted to wait on them for #20 to be finished. I do hope to get back to that work and finish it soon, but I have to work out some details of design first.

[sbaidon]

I would love to help on this if possible I just might need a bit of guidance!

[getify]

@sbaidon great, thanks! happy to have the help!

I want to hold off on adding hooks briefly, while I work on the re-org in #20. But hopefully this won't take too long to finish and unblock future hooks work. :)

[sbaidon]

Got it 👍

[getify]

hoping to give this some work this week. :)

[phenax]

@getify, Can I take this up?