version: Extend /etc/os-release

- Provide additional link for support and bug reporting.
- Use HTTPS links (related: "The IAB encourages all web servers to
employ TLS to protect their content, and use OCSP stapling to improve
the efficiency and privacy of revocation checking." [0].
- Add VERSION_CODENAME

[0]: https://www.iab.org/documents/correspondence-reports-documents/2017-2/iab-statement-on-ocsp-stapling/