Allow previous_tag specification on Release Form Automation

[thejeff77]

Would like to request an additional parameter previous_tag

Be added to the release form automation urls: https://docs.github.com/en/repositories/releasing-projects-on-github/automation-for-release-forms-with-query-parameters.

This would allow it to change from defaulting to auto to the specified tag in the URL.

Also consider allowing the passage of generate_release_notes=1 in a queryparam to do this as part of the page load.

This would come in handy for automation since the default generation only goes back to the last semantic version tag, even though the last formal release in the release list may have been well before the previous tag.

Eg: last release was at v1.5.1, when adding a release for existing tag v1.8.1, the auto option will diff back to v1.8.0 instead of v1.5.1. This is arguably ambiguous, and I'm not saying the auto calculation is wrong. Would be nice to be able to specify the previous tag however.

Thanks for any consideration!

[ThePeterDenham]

This is a lovely addition that helps with our automation and prevents incorrect release notes from being generated. It also doesn't seem like a massive piece of work. It's a shame that nothing has changed since this issue was raised in 2022.