New ports: x11-themes/freebsd-8k-wallpapers and x11-themes/freebsd-8k-wallpapers-kde

Collection of simple FreeBSD 8K wallpapers, and it also include a KDE branded variation.

Submitted by: Alexandre C. Guimarães <lebarondemerde@privacychain.ch>
Differential Revision: https://reviews.freebsd.org/D17266