Move documentation of endpoints to a docs directory

[Andrew-Murtagh]

What problem / inefficiency does your enhancement address?

If all documentation on the endpoints for every version of the API ends up in the main README it will become too large.

Describe the solution you'd like to see implemented

A docs folder with a different .rst file for every version of the backend. e.g. v0.1.rst, v0.2.rst, etc. These should be linked from the main README file.

Are there any alternative approaches?

Move all documentation outside of Github such as readthedocs.org, etc.

Who is requesting this feature?

@Andrew-Murtagh

Anything else?

Nope :)