Redirects twitter, reddit, youtube, medium, instagram to a proven-working open-source third-party frontend counterpart using https://farside.link/. Use the menu to enable/disable for specific sites

This script was modified from the original extension at https://addons.mozilla.org/en-US/firefox/addon/farside/ Reason for porting: I want to be able to disable it for specific sites at will.

It has permissions to view all websites so that you can still use the menu items when on a random proxy site, to disable the redirect so you can go back a page if you want to hit the original site.