Firefox fixes. Earlier versions could not start at all on Firefox: the background script called importScripts(), which does not exist in a Firefox event page, so it died before any of our code ran. This version fixes that, fixes every capture failing at the point of saving (Firefox refuses to download a data: URL, so the finished picture is handed over as a blob: URL), and the "Leave a review" button now opens this add-on's own page on addons.mozilla.org instead of the Chrome Web Store.

Every feature of this add-on has now been run in a real Firefox, not only checked by a linter.