Kustomize manifests for CRDs and snapshot controller?

[itspngu]

This repository is not very GitOps-friendly. While building and maintaining a Helm chart as suggested in #551 might be something that's not very high on the priority list, adding kustomization.yaml files to a few directories is neither a huge task nor does it require maintenance, and it would (at least for me and likely other users of automation frameworks like FluxCD) pretty much achieve the same thing - being able to install CRDs and controller from a versioned git repository.

I'll open a PR implementing this shortly.