Adds Github API wrapper for repos, pull requests, actions, etc. I went with a custom implementation because other Github API clients do not implement the Actions endpoints yet (an issue to watch: https://github.com/PyGithub/PyGithub/issues/1373). I also wanted something that would be simple and easy to work on instead of trying to extend an existing package with lots of inheritance that would be hard to debug.
Adds a script with functions for starting a CI/CD job and checking its status. This will be used by the cluster API endpoints.
Resolves #437