use readthedocs with pyproject

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 82.02%. Comparing base (2dfb069) to head (8b1d5bf).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## 3.0_develop #456 +/- ## ============================================ Coverage 82.02% 82.02% ============================================ Files 26 26 Lines 1363 1363 ============================================ Hits 1118 1118 Misses 245 245 ``` | [Flag](https://app.codecov.io/gh/ssl-hep/ServiceX_frontend/pull/456/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ssl-hep) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/ssl-hep/ServiceX_frontend/pull/456/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ssl-hep) | `82.02% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ssl-hep#carryforward-flags-in-the-pull-request-comment) to find out more.

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.