NJsonSchema uses unsupported Json Schema.

NJsonSchema, leans against draft 04, which for some properties, is not supported by AsyncAPI.

AsyncAPI specifically leans against draft 07, which refers to the validation rfc 01 (https://datatracker.ietf.org/doc/html/draft-handrews-json-schema-validation-01).

For instance, AdditionalProperties, is a map, not a boolean, in this draft.