Add SLSA generic generator workflow

[rizuashafiqi93]

This workflow generates SLSA provenance files for projects, satisfying level 3 requirements. It includes steps for building artifacts and generating provenance subjects.

[nginxproxymanagerci]

Docker Image for build 2 is available on DockerHub:

nginxproxymanager/nginx-proxy-manager-dev:pr-5316

Note

Ensure you backup your NPM instance before testing this image! Especially if there are database changes.
This is a different docker image namespace than the official image.

Warning

Changes and additions to DNS Providers require verification by at least 2 members of the community!

[jc21]

I don't entirely see the point of this workflow. This project doesn't publish artifacts, only a docker hub image that I build in my own CI, not in a github action.