[REQ] Allow referencing vendor extensions at the path level

Is your feature request related to a problem? Please describe.

I have the following two vendor extensions in my OpenAPI spec, x-foo-at-path-level and x-foo-at-operation-level:

    /pets:
      x-foo-at-path-level: true
      get:
        x-foo-at-operation-level: true
        responses:
          '200':
            description: A list of pets.
            content:
               ...

I'm able to reference x-foo-at-operation-level with the following in mustache:

{{#operations}}
  {{#operation}}
    {{vendorExtensions.x-foo-at-operation-level}} // able to reference this
  {{/operation}}
{{/operations}}

However, I'm not able to reference x-foo-at-path-level (or at least don't know how to).

Describe the solution you'd like

Please allow accessing the vendor extensions at the path level with {{../vendorExtensions.x-foo-at-path-level}} or similar syntax.

The issue names no file or test. Start by tracing how operation-level vendor extensions are exposed to Mustache templates, then compare that context with the path-level data available during generation. Done means a path-level extension is accessible from the template context as described, with coverage for the provided OpenAPI example.