Handle "oneOf" { "required" ... }

"Required" isn't always a yes/no condition in the glTF schema. Some types like [image](https://github.com/KhronosGroup/glTF/blob/41657440949864444672b8a2776b7c5086ad90e5/specification/2.0/schema/image.schema.json#L40-L43) have a "one or the other is required" kind of condition, that is not reflected in the documentation.

This tool should find a way to output that detail.

Start with the linked image.schema.json example and inspect how wetzel currently turns JSON Schema required rules into Markdown. Determine how the oneOf alternative requirement should appear in generated documentation; done means the output preserves that requirement rather than presenting it as a simple yes/no condition.

Written by the indexing model from the issue text.