Enter the new world of GitHub actions [1]/GitLab pipelines [2]. This
simplifies our end of the infrastructure considerably:
* No need any more to set up webhooks, all the relevant configuration
is right in the workflow file.
* Does not need any infrastructure on our side any more, and thus works
for third-party projects. They just need to set up their own secrets.
* GitHub automatically provides a temporary `GITHUB_TOKEN` with
sufficient write access to the project to publish a release, so we
don't need to carry around that secret. Thus if your project only
releases to GitHub, there is zero secrets management.
Also adjust cockpituous-release a bit (update Fedora version, fix
project name copy-pasta), point to the action workflow and necessary
secrets.
Closes#380
