tools: add GitHub Action to run find-inactive-collaborators.mjs

Add a GitHub Action for find-inactive-collaborators.mjs that will run it
and list collaborators who have been inactive for more than a year. It
will run when manually triggered by a collaborator and on a schedule of
once a month.

PR-URL: https://github.com/nodejs/node/pull/39335


Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: James M Snell <jasnell@gmail.com>