[roadmap] JSON Schema (draft 2020-12) bridge for the validator

[Cryptoteep]

Goal

The built-in validate() uses a lightweight custom schema format. Many users already have JSON Schema files. We should provide a bridge that converts a (subset of) JSON Schema draft 2020-12 into our internal SchemaNode tree.

Proposed API

import { validate, fromJsonSchema } from 'jsoncraft';
const schema = fromJsonSchema(jsonSchemaDraft2020);
validate(data, schema);

Scope

Support the common keywords: type, required, properties, items, enum, minimum, maximum, minLength, maxLength, pattern, default.

Complex keywords ($ref, oneOf, allOf, conditional subschemas) can come later.

Acceptance

• fromJsonSchema() converts a draft-2020-12 schema into SchemaNode
• Round-trip validation matches the behavior of Ajv for the supported subset