Add guide for old Winamp look for Audacity

This adds even more nostalgia

All that has to be done is putting this file
https://skins.webamp.org/skin/5e4f10275dcb1fb211d4a8b4f1bda236/base-2.91.wsz/
or this file
https://www.gnome-look.org/p/1008329/

I would call them something like `winamp-classic.wsz` and `audacious-classic.wsz` when adding them to the repository

to `.local/share/audacious/Skins` (create it if doesn't exist)
after that it can be selected in settings->appearance

The first one is classic winamp all the way, the second keeps the name audacious in the title and the audacious icon.