Document debug packages
This makes it simpler to link to a more complete setup.
The situation is not ideal since we lack proper packages for amber itself so they need to be fetched from Debian (https://tracker.pureos.net/T873).
There also deviations for byzantium since squeekboard (/cc @dorota.czaplejewicz ) and chatty (/cc @mohammed.sadiq ) are still outdated there (hence tripping up other debug packages) so i had to leave that out too.
Closes: #158 (closed)
Edited by Guido Gunther