JSON Schema Draft 2019-09 Support

We would like to support JSON Schema Draft 2012-09 in addition to [Draft7](https://github.com/kson-org/kson/pull/186) and [Draft 2020-12](https://github.com/kson-org/kson/issues/204).  See https://github.com/kson-org/kson/pull/203 for some notes/inspiration for approaching this.