feat(fakers): ability to add fakers

[bartoszmajsak]

As mentioned in #7 I am playing with fuzzy testing and for that I'm using https://github.com/json-schema-faker/json-schema-faker. I wanted to have an option of adding fixer fields while generating the schema, so I can influence how particular field is generated. I'm aware this can be done as part of OpenAPI extension in k8s upstream, but was wondering if we couldn't have this flexibility at this level for testing purposes.