We should use the staging files instead of having some files
authoritative in the external repo. Otherwise, we complicate the
publishing process as it has to know which files come from the latter.
`README.md` and `LICENSE` are authoritative in external repos.
We should move them to staging.
- add usage instructions
- add Use Cases, Defining Types and Clean Up section. Copied
from apiextensions-apiserver/examples/client-go. This is done
to be consistent with all other examples.
- fix formatting
Kubernetes-commit: cdcc6ac3751ab7b04bda5bcd5fc82d236d940cc5
