README and `docs/source/index.rst` do not agree on REST API

[jwodder]

Currently (as of commit 9351c88), the descriptions in the REST API in README.rst and docs/source/index.rst do not completely agree. In particular:

• Only docs/source/index.rst documents the following endpoints:
  • /projects/{project_id}/subjects/{subject_id}/instruments
  • /projects/{project_id}/subjects/{subject_id}/derivatives/
  • /subjects
  • /subjects/{subject_id}
  • /dataelements
  • /dataelements/{dataelement_id}
• Only docs/source/index.rst states that /projects and /projects/{project_id} can take a fields query parameter

[yarikoptic]

after the difference figured out and fixed -- we should "deprecate" README.md as a copy of docs/source/index.rst and keep detailed info within docs (and probably post rendered version on RTD). Ref: https://github.com/incf-nidash/PyNIDM/pull/357#discussion_r1185210317

[yarikoptic]

apparently there is an RTD project already setup and there is https://pynidm.readthedocs.io

[jwodder]

@yarikoptic The docs build is failing, though, so the updates in #357 aren't taking effect. I would need access to the project on Read the Docs in order to figure out what's going on.

[jwodder]

The docs are building again now.