Take a pass at docstrings

[lread]

Currently

I'm a newish maintainer on clj-yaml and I don't totally understand its public API yet.

So...

What I typically do in this scenario is take a pass at a libs' public API and describe in docstrings as I learn. This not only helps me to ramp up but also helps serve as a useful future reference for me (and hopefully others). The current clj-yaml docstrings are on the very sparse side but the API is small so should not be too much effort.

This might also involve reviewing/updating the user guide (which is currently included in the README), but also, maybe not.