Support new API to Request a CVE for a repository security advisory

[gmlewis]

GitHub Blog post: https://github.blog/changelog/2023-08-03-request-a-cve-identifier-for-your-repository-security-advisory-via-rest-api/
Rest API docs: https://docs.github.com/en/rest/security-advisories/repository-advisories?apiVersion=2022-11-28#request-a-cve-for-a-repository-security-advisory

This would be a great PR for any new contributor to this repo or a new Go developer.
All contributions are greatly appreciated!

Feel free to volunteer for any issue and the issue can be assigned to you so that others don't attempt to duplicate the work.

Please check out our CONTRIBUTING.md guide to get started. (In particular, please remember to go generate ./... and don't use force-push to your PRs.)

Thank you!

[be0x74a]

Hey @gmlewis can I pick this one?

[be0x74a]

Opened the PR, hope that's okay :)