panic on `$ref` to any path that is not `"#/$defs/xyz`

I ran into a panic when running cargo typify ldtk-1-5-3.json (cargo-typify v0.1.0),

It's the same not found ref #/SomeObject is missing from #299, but this time without recursion needed, just a maybe unexpected indirection.

The application panicked (crashed).
Message:  $ref #/LdtkJsonRoot is missing
Location: typify-impl/src/convert.rs:1183
  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ (BACKTRACE...) ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

The Ldtk JSON Schema v1.5.3 uses a reference to its root object.
I'm not sure if this is legal, but LDTK already generates code using QuickType, so I guess they at least allow it.

Here's an overview of the schema,

  {
  	"$schema": "https://json-schema.org/draft-07/schema#",
  	"description": "This file is a JSON schema of files created by LDtk level editor (https://ldtk.io).",
  	"title": "LDtk 1.5.3 JSON schema",
  	"version": "1.5.3",
  	"$ref": "#/LdtkJsonRoot",  // <----  (Is this legal?)

  	"LdtkJsonRoot": {/* ... */},  // <--/--

  	"otherTypes": {/* ... */}
  }

Start with the reproducer command cargo typify ldtk-1-5-3.json and inspect typify-impl/src/convert.rs:1183, where the missing $ref panic is reported. Compare the root $ref and LdtkJsonRoot in the LDtk 1.5.3 schema; done means this schema no longer panics and the command completes successfully.