link: support link variations through query parameter

[McShelby]

Currently it is possible to link to other languages by prepending the link with the language prefix like pir/basics.

This is pretty hacky and would collide if there is a pir page in the current translation.

Also it is currently not possible to link to other output formats of the same page.

By providing query parameter for both cases and respecting them in the link render hook, both could be supported in a much cleaner way.

This was discussed in https://discourse.gohugo.io/t/relearn-theme-include-a-reveal-slide-per-topic/49583