Allow generation of schema types for any schema

[olensmar]

I would like to create a validator for kustomization files - but the codegen requires a CRD to generate schema types. Suggest we support generation of types for any json-schema provided in a src/schemas/plain folder - named after the schema file itself.

Follow-up question is if we should support parsing/validation of any YAML file - in which case the Resource object would have to be modified accordingly and name, apiVersion, kind would be optional?