Can't install addons that require Firefox 61+

[theel0ja]

For example, https://addons.mozilla.org/en-US/firefox/addon/refined-github-/

[intika]

This is because of resist fingerprint feature and and probably also the zero communication feature. i will probably add a switch for mozilla addon page.
I added this to #3 and it will be followed there...

Thank you for reporting that :)