[BUG] [Typescript] Response headers are not available.

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
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Description

I want to access the response headers for an E-tag. In the openAPI yaml file, the headers are defined for the response but it doesn't generate anything to access them

      responses:
        '200':
          description: Resource returned OK.
          headers:
            Cache-Control:
              $ref: '#/components/headers/CacheControlHeader'
            ETag:
              $ref: '#/components/headers/ETagHeader'
            Version:
              $ref: '#/components/headers/VersionHeader'
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/....'

the header is defined as follows:

    ETagHeader:
      description: 'Caching: An opaque string which identifies a specific version of the returned resource.'
      schema:
        type: string

The problem with the headers in the response not being accessible (especially E-tag) seems to be faced by other typescript-xxx client generators https://github.com/OpenAPITools/openapi-generator/issues/6527

Start with the TypeScript client generators and the supplied OpenAPI response definition, then inspect how generated responses expose headers. Confirm the behavior across the affected typescript-xxx generator and add access to the ETag and other declared headers; done means a generated client can read them from the response.