Add support for Enterprise GitHub

Thanks for this utility.

Can I request you to please add support for Enterprise GitHub?

By default Octokit goes to api.github.com and there is no provision to pass baseUrl to it. It would be great to add baseUrl via env from GitHub Actions, for example.

Start by locating where Octokit is initialized and how GitHub Actions environment variables are read. Verify how Enterprise GitHub supplies its API base URL, then confirm that the action can use that value and complete a request against an Enterprise endpoint.

Written by the indexing model from the issue text.