Spec out the API for js-polykey

[CMCDragonkai]

We need to spec out the function types for js-polykey and the data structures that we are managing.

I've written notes on this in the Polykey repository, but they are all over the place and involve some older ideas. Hopefully @ll-aashwin-ll can clean them up and a better spec.

https://github.com/MatrixAI/PolyKey

See README.md, README2.md... etc.

We can discuss the spec here and eventually write them into the code. This js-polykey can be the first reference implementation.

[MeanMangosteen]

Since Polykey will predominantly have IO bound operations, we should definitely have async methods in the API.

From #9

Since the Polykey api does not have to preserve any existing API method signatures, like efs does with fs, it can use modern promise primitives for async methods instead of callbacks.

This will provide a much cleaner and future proof API.

Is it still worth having sync methods in polykey?

[CMCDragonkai]

No it should just focus on async methods.

[CMCDragonkai]

This issue could be closed soon with a spec for the Polykey api. At least an initial spec that we can iterate on. It can be in the docs directory. But generated docs is different from written docs. We would need to separate the 2.