feat(os): Add intial build instructions for kOS

Introducing kOS after searching for a good Kubernetes system base for
way too long. Mostly based on the `osbuild` project instructions with
the needed adjustments. Collected some lessons learned from my past 2
days.

References:
https://www.osbuild.org/guides/user-guide/building-ostree-images.html
https://github.com/osbuild/weldr-client#package-sources
https://copr.fedorainfracloud.org/coprs/sheogorath/kubernetes-1.22/