Adds a new `-g` parameter so that output will also include the GitHub
username.

This change uses a simple regular expression as opposed to directly
returning the original line from the file to make the extraction of
GitHub usernames more robust to other changes on the line in the
maintainers text file.

Signed-off-by: Michael Kubacki <[email protected]>

Adds a script that provides GitHub API helpers for workflows and
other GitHub automation in the repository.

Signed-off-by: Michael Kubacki <[email protected]>

Adds a new GitHub workflow to automatically add reviewers to pull
requests when they are opened, reopened, synchronized, and if a draft
pull request is marked as ready for review. The workflow will not
run on draft pull requests.

The workflow is meant to be simple to understand and modify, relying
on existing logic in GetMaintainer.py to determine the relevant
reviewers and using simple Python GitHub REST API wrappers with the
default GitHub token for authentication.

Future changes may optimize the workflow.

Signed-off-by: Michael Kubacki <[email protected]>