Add JSON schema to schema registry.
JSON Schema supports [Draft 03](http://tools.ietf.org/html/draft-zyp-json-schema-03), [Draft 04](http://tools.ietf.org/html/draft-zyp-json-schema-04) and [Draft 06](https://datatracker.ietf.org/doc/html/draft-wright-json-schema-00).