add Firefox add-on Hacker News Reader

I've written a Firefox add-on [Hacker News Reader](https://addons.mozilla.org/en-US/firefox/addon/hacker-news-reader/) that makes extensive use of the Algolia HN Search API. I would appreciate it if you could add this add-on to your list of [cool apps](https://hn.algolia.io/cool_apps). The code is in my [Github repo](https://github.com/pragmatictester/hnreader).