Needs a quick start section in the README

[thomashoneyman]

Is your change request related to a problem? Please describe.
As described in the documentation section of the Library Guidelines, Contributors libraries are expected to have in their README a short summary of the library's purpose, installation instructions, a quick start with a minimal usage example, and links to the documentation and contributing guide.

This library currently doesn't have a completed quick start in the README.

Describe the solution you'd like
The library needs a quick start section after the installation instructions. machines is a good example of a small, to-the-point quick start.

We could at least demonstrate a minimal example which uses suspend, fork, join, and kill.

Additional context
See the Governance repository for more information about requirements in the Contributors organization.

[thomashoneyman]

The library summary could also stand to improve -- when should you reach for this library? What are some example monads with instances? I'm only aware of Aff.

[natefaubion]

It essentially lets you write generic concurrency code for either Aff or things that are equivalent to ReaderT e Aff a.