Add Arch Linux logo

As per Arch Linux Trademark Policy[0], the logo can be used since it matches the requirements at "advocacy" term.

Let me know if I need to get an official statement from Arch Linux. Do I need to do something at osinfo-db? It seems there is already data for Arch: https://gitlab.com/libosinfo/osinfo-db/-/tree/master/data/os/archlinux.org

thanks!

[0] https://wiki.archlinux.org/index.php/DeveloperWiki:TrademarkPolicy#Permitted_Use