Mention the easy-routes add-on in the doc.

[vindarel]

No description provided.

[stassats]

I cannot vouch for the quality or list all the competing third party extensions in the docs, so it'd probably be better to document them somewhere else.

[vindarel]

Ok. Note that I don't want to add all of them (there's the new https://github.com/moderninterpreters/hunchentoot-multi-acceptor/ for example, which I reference somewhere else), but this one fills a gap, is used and its author has some background.

[stassats]

I don't want the documentation to look like it's endorsing a particular project, especially when I have no knowledge of it.