Update API docstrings

[teald]

Summary

This PR updates documentation for the API functions and classes, including examples where necessary.

Documentation changes

• Unify Parameters -> Arguments in docstrings
• Add Examples as appropriate
  • Not explicitly requested, but this is extra insurance against documentation/example changes
• Imperative mood for summary line
• Single-line summary lines
• Specify "numpy" convention for linting in pyproject.toml

Other changes

• Deprecate add_header_to_table, as its implementation is no longer used in astrodata and is not recommended.

Notes

• This is meant to address requests for examples/clarifying documentation in astrodata pyOpenSci/software-submission#181