Add workaround for AUR downtime, with using github aur mirror

[ptr1337]

Hey!

In the recent months the AUR has been affected over and over again from DDoS attacks, which resulted into downtime there. This impacts the user expierence heavily.

Archlinux does provide a mirror of the AUR git repository, which utilizes the branches of each package.

The Github URL:
https://github.com/archlinux/aur

[fosskers]

For metadata at least I use my own server, but it's true that pulling the actual packages comes from the AUR itself. There's potential to allow a fallback.

[roussak]

Heh!.. Maybe, the Microsoft is that who DDOSing Arch (aiming to move AUR to github)?..

IT'S A JOKE! Because, I can't find out any reasonable explanation for this outrage.