Add pydocstyle to PR checks

[nawatts]

pydocstyle is currently configured as a pre-commit hook. However, it would be good to run it on pull requests as well since some contributors may not have pre-commit hooks set up.

This PR...

• Adds pydocstyle to requirements.in/requirements.txt so that we can pin the version used in PR checks and use the same version in PR checks as in pre-commit hooks.
• Moves pydocstyle configuration to pyproject.toml so that PR checks and pre-commit hooks use the same configuration. This required updating pydocstyle.
• Removes the blanket ignore of rule D103 (public functions must have docstrings) and replaces it with specific ignore comments on main functions in scripts.
• Adds pydocstyle to the CI workflow run on PRs.

Related to #21

[klaricch]

Thanks Nick!