Automate contributor list via GH Actions

[PeterBowman]

I'd like to add a workflow to launch our update-contributors.py script (introduced in #47).

Dispatch options:

• manual
• whenever dev-aliases.yml is updated

[PeterBowman]

Done at:

• 9d02831
• 2bbb681
• 0e70a01
• 2037934

A new contributors.yml workflow runs the update script (either on demand or following an edit in dev-aliases.yml), tests whether docs/contributors.md was changed and, if true, commits and pushes the changes, then calls the gh-pages.yml workflow to regenerate the static site on GH Pages.

Refs:

• https://docs.github.com/en/actions/using-workflows/reusing-workflows#calling-a-reusable-workflow
• Unable to find reusable workflow github/vscode-github-actions#254 (linter error in web editor and VS code)

I created a new personal access token (PAT) with the permissions detailed here: #47 (comment). Keep in mind it lasts only one year due to limits on the maximum expiry time. I'd rather use GITHUB_TOKEN (with extended permissions if necessary), but this is not possible at the moment: https://github.com/orgs/community/discussions/46566. This token is accessed through the DEV_MANUAL action secret (org settings).