Support linting more than the commit message itself

I would like to create a plugin for commitlint that would lint the committer/author email to only allow email domains from a list i.e. company emails only and possibly another to make sure commits are signed.

Would a PR that adds some fields to the `parsed` variable in the rules function be welcome?

Are there better ways of doing this maybe and it's not interesting to add support for it in commitlint?