Expose code coverage stats in repos #4

The repos within the org generally have code coverage run during CI (e.g., https://github.com/unikorn-cloud/identity/actions/runs/13947449650/job/39037904691), but the information is not exposed.

We should be able to get it to display a status item for pull requests (see https://docs.codecov.com/docs/quick-start#step-5-get-coverage-analysis-from-codecov), at least, which would be helpful.