Migrate data from Maintainers.txt to the GitHub standard CODEOWNERS
files plus REVIEWERS and CONTRIBUTORS.md. The latter file contains
mappings from name to email address and GitHub usernames, which will
help people who want to email maintainers instead of using GitHub.

Add .github/workflows/AssignReviewers.yml which adds reviewers to a
Pull Request based on the content of the REVIEWERS file.

Signed-off-by: Rebecca Cran <rebecca@bsdio.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>