Since Firefox team has implemented the same browser extension API that Chrome has, we decided that we could also publish Web Scraper on Firefox. Without much effort we got Web Scraper running.
You can install the Firefox addon from here - https://addons.mozilla.org/en-US/firefox/addon/web-scraper/ . If there is something that doesn't work the same way it works in Chrome leave a comment here.
Also big thanks to Firefox team for making the web extension API.