[monarch][debugger] Add OSS debugging example + README

Pull Request resolved: #820




@imported-using-ghimport

Differential Revision: [D80032270](https://our.internmc.facebook.com/intern/diff/D80032270/)

**NOTE FOR REVIEWERS**: This PR has internal Meta-specific changes or comments, please review them on [Phabricator](https://our.internmc.facebook.com/intern/diff/D80032270/)!
ghstack-source-id: 302232568

Author: samlurye