Enable Codecov for test coverage reporting on public repo

Hi @RCapellan, I'm working on adding test coverage reporting for the harmonize-tools package and would like to confirm whether we can enable Codecov integration for the project. Although the repository is public, development is still in the early stages and not fully active yet. When trying to upload coverage results using covr::codecov(), I get the following error:

Upload failed: {"message":"Token required because branch is protected"}

Possible solutions: Enable Codecov for this public repository. Since it's public, Codecov should work for free and without a token, as long as the branch is not protected. If the branch must remain protected, we can: Create a Codecov token for the project. Add it to the GitHub secrets as CODECOV_TOKEN, so uploads work from protected branches. Alternatively, during early development, we could use a non-protected branch to simplify coverage uploads. Please let me know what you think. I’d be happy to help set up the initial integration if needed. Best regards c.c #16 #21