Add CI

[nirs]

In the long term, it would be nice to run every sample on all the environments it can run on. This ensures that any change in the sample is correct. But we can start with something much simpler and extremely fast, make sure that every kustomization overlay can be create using kustomize build. This would prevent stupid errors that are hard to find during reviews.

Tasks

• workflow
• yamllint to keep the yaml consistent
• markdownlint to keep the docs consistent
• kustomize build for every overlay, including base overlay
• labels (e.g every OCM resource has app= label)
• spell check?