contrib/debootstrap: Add initial support for Tanglu

This will add support for Tanglu, a Debian based Linux-distribution.

Docker-DCO-1.1-Signed-off-by: Matthias Klumpp <matthias@tenstral.net>
trivial: Remove end-of-line whitespaces from mkimage-debootstrap

Docker-DCO-1.1-Signed-off-by: Matthias Klumpp <matthias@tenstral.net>