fix(docs): update doc, codespaces config and GHA on commit GPG signed (…

…#860)

# Description

* update contributing doc to add a note about signing commits by default
* add instructions for  codespaces users to use GPG to sign commits

## Related Issue

If this pull request is related to any issue, please mention it here.
Additionally, make sure that the issue is assigned to you before
submitting this pull request.

## Checklist

- [x] I have read the [contributing
documentation](https://retina.sh/docs/contributing).
- [x] I signed and signed-off the commits (`git commit -S -s ...`). See
[this
documentation](https://docs.github.com/en/authentication/managing-commit-signature-verification/about-commit-signature-verification)
on signing commits.
- [x] I have correctly attributed the author(s) of the code.
- [x] I have tested the changes locally.
- [x] I have followed the project's style guidelines.
- [x] I have updated the documentation, if necessary.
- [x] I have added tests, if applicable.

## Screenshots (if applicable) or Testing Completed


![image](https://github.com/user-attachments/assets/0bec8adb-dcf7-46c0-aedf-466306d99c1f)

## Additional Notes

Add any additional notes or context about the pull request here.

---

Please refer to the [CONTRIBUTING.md](../CONTRIBUTING.md) file for more
information on how to contribute to this project.

---------

Signed-off-by: Simone Rodigari <[email protected]>

docs/07-Contributing/developing.md

@@ -190,6 +190,10 @@ In order to certify the provenance of commits and defend against impersonation,
 Documentation for setting up Git and Github to sign your commits can be found [here](https://docs.github.com/en/authentication/managing-commit-signature-verification/signing-commits).
 Additional information about Git's use of GPG can be found [here](https://git-scm.com/book/en/v2/Git-Tools-Signing-Your-Work)
 
+> To configure your Git client to sign commits by default for a local repository, run `git config --add commit.gpgsign true`.
+
+For **GitHub Codespaces** users, please follow [this doc](https://docs.github.com/en/codespaces/managing-your-codespaces/managing-gpg-verification-for-github-codespaces) to configure GitHub to automatically use GPG to sign commits you make in your Codespaces.
+
 ### Developers Certificate of Origin (DCO)
 
 Contributions to Retina must contain a Developers Certificate of Origin within their constituent commits.