docs: Page for each function, document python with doc strings.

[odscjames]

https://github.com/Open-Telecoms-Data/lib-cove-ofds/issues/23

[odscjames]

See at https://libcoveofds.readthedocs.io/en/2022-11-23/geojson_to_json.html

Not great docstrings, but this sets up pages and the RTD environment, so better than current docs!