Thanks for your review. We have to rely on the community when it comes to adding new languages. Unfortunately, adding support for a new language is more complicated than adding a list of words, which limits the number of people willing to work on this.

About this website (addons.mozilla.org) not working - it's a hard restriction by Firefox. As far as I know, no add-on that requires access to the HTML page will work on addons.mozilla.org.

1.0.10 has just been released and should fix the most prominent issue. Saving the preferences still does not work. Update 2017-04-15: everything should work fine now again with version 1.0.13