bug(json-schema): `JsonSchema.fold` without importing `json-schema-types` raises a TypeError

[ahrjarrett]

To reproduce this bug, comment out line 2 in this sandbox.

Doing so raises this TypeError:

The inferred type of 'fromJsonSchema' cannot be named without a reference to '../../node_modules/@traversable/json-schema-types/dist/dts/types.js'. This is likely not portable. A type annotation is necessary.

It looks like there's some transitive type-dependency that's not crossing the package boundary, and the re-export isn't helping.