Create, use, and advertise a kops-announce mailing list

Please create a kops-announce (or similar) mailing list, like the [kubernetes-announce list](https://groups.google.com/forum/#!forum/kubernetes-announce) used by Kubernetes.

It would be useful to me and doubtless to other members of the community to be notified when new Kops versions are released or when critical bugs or security vulnerabilities are discovered in Kops.

No repository files or tests are identified. Start by reviewing the Kubernetes announce list linked in the issue and the project's existing release and security notification practices; done means a kops-announce list exists and its use for version releases, critical bugs, and security vulnerabilities is documented and advertised.

Written by the indexing model from the issue text.