Add JSON schema to the Custom Resource Definition

[grossvogel]

There's already a schema for the .review_bot.yml file in the app repo, which maps to spec.config in the CRD.

In this case that'll just be a (large) portion of the CRD schema, but the CRD contains a bit more around the GitHub repo, pull request, etc.

• Need to get a handle on how exactly to include the schema in the CRD definition, assuming that's something our versions of k8s let you do at all.
• Is there a way to reference the other schema instead of maintaining two copies? (Note that the CRD schema appears to have some extra rules around making sure the schema is "structural.")
• Is there a way to tell Bonny's generator to include our schema info when it generates the CRD? Looks like maybe not yet, which might mean we'd need to hack up our own generator for the CRD manifest :(