Guide: minimalistic KDE, SDDM and NetworkManager setup

[Screenager]

This is should be useful for people who chose a amd64/desktop/plasma profile, simply follow the guide to get a working baseline KDE Plasma desktop environment:
https://wiki.gentoo.org/wiki/User:Scree ... KDE_PLASMA
I included instructions up to a working browser and optional flatpak support. This should provide a solid base to explore and use gentoo as a daily driver.

[Screenager]

Did some minor changes, it is up to date and working with Plasma 6