Initial exploration into an async check

[davidnormo]

Following on from #45

All credit for the async quick-check implementation goes to promesa-check ⭐️

This PR adds this behind a new function: checkAsync. This acts exactly the same as check except that the property function needs to return a promise.

Ideally I'd prefer check to be able to accept both sync and async properties, which I may work on, but thought I'd share this for some early feedback

[leebyron]

Thanks for doing this! Very cool to see the async check implementation out there, that definitely simplifies some things.

Some next steps I can see:

• Looks like check and checkAsync are largely the same - perhaps there is some code reuse to be had?
• Tests are pretty sparse - I'd love to see tests for returning false, throwing an error, and rejected promises.
• It would be really cool if check operated on sync or async properties, returning a Promise in the case of async properties, though perhaps that could be saved for a future PR.
• Test runner integrations here would be nice as well - let's make sure that async or (done) tests in appropriate runners do the right thing.
• We'll want to make sure the flow and typescript type definitions (found in /type-definitions) are up to date with this change