Add an export swagger/oas option

[giordanolucas]

Since a lot of the people looking at the API docs are programmers, it would be great to provide an autogenerated OAS spec to download in the documentation.

This would not only be a great documentation feature, but also allows the users to easily connect to the server using a lot of already existent software that knows how to parse OAS specs.

And since all the data for generating the OAS is already there, I don't think this would be an issue.

What do you think?

[MikeRalphson]

Generating arbitrary markdown from OAS is reasonable, the other way around would be a much harder proposition.