[hoanle0126]

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

Description

Fixes #157

Currently, env-schema re-exports Ajv's JSONSchemaType<T> directly. Because env-schema registers the custom modifying separator keyword on type: 'string' schemas to split strings into string[] at runtime, typing an interface property as string[] while defining its schema as { type: 'string', separator: ',' } fails TypeScript validation (Type '"string"' is not assignable to type '"array"').

This PR updates envSchema.JSONSchemaType<T> so properties typed as string[] (or readonly string[]) in T accept either a standard array schema or a type: 'string' schema with a required separator: string property, while preserving automatic generic return type inference on envSchema({ schema }).