Support Custom Maintainer Fields

[Alexhuszagh]

It would be nice to offer support for maintainers in projects that are Javascript-based. I understand that this could be difficult to implement if it would read the package.json equivalent for each language (Cargo.toml for Rust, setup.py for Python, etc.), so it would be nice if you could manually specify maintainers on the command-line. Another approach would be to read package settings for common programming languages.

For example:

weallbehave \
    --maintainers='{"Alex Huszagh": {"email": "...", "twitter": "..." }}'
    > CODE_OF_CONDUCT.MD

This way, the maintainers field can be piped provided in JSON, piped in from any file, and this would support many different project types.