Cannot parse the openapi specification itself

Hi, trying to parse the OpenAPI v3.1 specification itself fails with the following error message:

cargo typify ./openapi31.json
The application panicked (crashed).
Message:  not yet implemented: invalid (or unexpected) schema:
{
  "type": "object",
  "additionalProperties": {
    "$ref": "#/$defs/path-item-or-reference"
  },
  "$ref": "#/$defs/specification-extensions",
  "$comment": "https://spec.openapis.org/oas/v3.1.0#callback-object"
}
Location: /home/kasper/.cargo/registry/src/index.crates.io-6f17d22bba15001f/typify-impl-0.0.16/src/convert.rs:700

This library seems awesome. I had hoped to able to use it to work with the openapi spec in code. I don't know much about the details of the above error message however. Is this like a single bug (i.e. it should work) or is this a very complicated file (i.e. this is far off and not expected to work at the moment)?

Reproduce the failure with cargo typify ./openapi31.json using the linked OpenAPI 3.1 schema. Start from the reported schema-conversion panic in convert.rs and determine how the callback object schema is handled; done means the specification parses without a panic and the relevant behavior is covered by a regression test.