V2: Implement the @Produce comment

[Nerzal]

Is your feature request related to a problem? Please describe.
In V2 the @Produce comment is currently being ignored.

Describe the solution you'd like
Parse the @Produce comment and append the listed types to the specification

Describe alternatives you've considered
None.

Additional context
As OpenAPI 3.1.0 supports more fields etc. than swagger 2.0 we should deprecate the @Produce comment in the future and replace the behavior with something else. But for the sake of being non breaking backwards compatible we should implement it now.