Thank you for your work but please update the requirements because most versions of your add-one require WebExt and when you install it with an older FF version than 57, it's allowed by addons.mozilla.org but you get an error message "the add-on appears to be corrupt". I've spend some time to find how to solve this error and it's only because the requirement description is wrong and only versions prior to 2 can be installed on FF 56.