I'm unsure about adding these as pre-reqs.  I think stuff listed under `Prereqs / TestRequires` is supposed to be things required just to run the test suite of the distribution being built - so they might or might not actually get installed; if they don't, then the new functionality won't work for users apps.

I'm thinking as this is an optional extra feature we should perhaps not list them as pre-reqs (maybe as recommends, though), and have the `Dancer2::Test::route_pod_coverage()` code attempt to load them safely, and skip tests if they're not available.

I'd like inputs from the other devs on this one.