Supporting standard `---` convention for comments to not be included in public APIs

We recently had a PR https://github.com/elastic/cloud-on-k8s/pull/8020 where we wanted to include a comment in a public CRD, but didn't want it to be included in the public-facing API docs. It seems that the [controller-tools](https://github.com/kubernetes-sigs/controller-tools/pull/877) supports using `---` to preface comments to not be included. I think this tooling may want to support this as well to be consistent.