Permit configurable scopes (e.g. workflows)

[cboettig]

Proposed change

Consider adding a cli option to request additional scopes? Currently, it looks like only the repo scope is set, and this choice is hardwired:

https://github.com/jupyterhub/gh-scoped-creds/blob/main/gh_scoped_creds/__init__.py#L23

Note that this means that users cannot push to repositories modifications to .github/workflows, as I believe that requires the "workflows" scope as well.