Merge `setup.cfg` into `pyproject.toml`

[edthedev]

setup.cfg does require wheel_inspect.

install_requires =
  requests
  wheel-inspect

Per discussion, we may want to refactor to merge setup.cfg into pyproject.toml for maintainability.

Note: See approach in awscli-login, where setup.cfg is no longer in use.

Originally posted by @edthedev in #29

Tasks

• remove setup.cfg
• add to pyproject.toml as needed to restore any lost configuration from setup.cfg
• verify local tests succeed (make test)
• verify local build succeeds
• verify CI/CD in GitHub Actions succeeds

[edthedev]

Possibly useful for reference: techservicesillinois/awscli-login@2cda447