Request to support query parameter for search query

[jfmengels]

(Duplicate of #144, but creating a new issue since duplicates are appreciated)

As part of elm-review's documentation, I need to tell people how to find plugins for elm-review, which I do by telling them to go to the package registry website and look for elm-review- (which is the naming convention).

It would be a lot nicer to be able to have a link to the package registry with that search query pre-filled. As far as I know, the easiest way and most common way to support that is by supporting a query parameter in the URL.