Why do we need this ?

I would like to use this tool with an internally hosted GitHub instance.

Acceptance Criteria

I would be OK with this being something that can be set via env-var or config file.
It does not need to be something that supports live-reloading or even something that's likely to be changed often.

Further Comments / References

Nothing immediately comes to mind; it should just be a hostname change. Nothing about the API changes with self-hosted.