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Describe the bug

Starting from OAS 3.1.0, the externalValue should allow relative reference, See the documentation

To Reproduce

1. Create a schema as following using openapi:3.1.0

Response:
      description: OK
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/ResponseSchema'
          examples:
            jsonObject:
              externalValue: "./components/response.json"

2. Attempt to use spectral to validate this schema with spectral:oas rule.
3. Validation failed with

error  oas3-schema            "externalValue" property must match format "uri".

Expected behavior
Spectral validation should pass and allow for relative URLs