Release-perform: differentiate between releases and pre-releases

[dmlloyd]

It would be nice if the release-perform action would create the GitHub release as a "pre-release" if the version ends with e.g. alphaN or betaN. Not super critical, just something I noticed.

[gastaldi]

This should be implemented in https://github.com/radcortez/milestone-release-action AFAIK, and it happens in the release prepare workflow