More example to advanced distros

[Nibodhika]

I read the contribution guide and know that the idea is to only show the top 10 distributions on distrowatch, but having Arch as the sole example of an advanced distribution feels incomplete, almost as if it were the only example. Not to mention that Arch is not even on the top 10 anymore, so if this rule were to be followed the list would have no example of an Advanced Distro.

I propose Slackware and/or Gentoo get added, since they're very well known (both being at the top 50) and the usual examples of an advanced distribution.

[ixzh]

I second Void!