Suugestion: remove tracking de-refer prefixes

[tseeling]

Some webmail frontends prefix links in mails with a tracking URL. Allegedly this is for antivirus but of course it also allows tracking.

E.g. german company gmx.net does this. Changed URL in email looks like this:

https : // deref-gmx . net/mail/client/PilesaN1F6U/dereferrer/ ? redirectUrl=https%3A%2F%2Fgitlab.com%2Fusers%2Fconfirmation%3Fconfirmation_token%3Ddummytoken

The addon should remove everything from the start of the URL up to redirectUrl= and decode the entities to make it a valid URL again.