"Mixin" layer for adding latest Docker versions into the Yocto Project LTS.

This is a supplementary layer to dunfell/go branch of meta-lts-mixins. As that
layer updates go toolchain to newer versions, this renders the docker recipes
from dunfell branch of meta-virtualization unbuildable. The purpose of this layer
is to backport latest, compatible docker from meta-virtualization master to
dunfell.

Maintainers:
Alexander Kanavin <alex@linutronix.de>