Draft: DEP-18: Enable true open collaboration on all Debian packages

This is an early draft posted for visibility here as MR and on mailing list in https://lists.debian.org/debian-devel/2024/07/msg00429.html.

Summary:

1. Have package source code in version control, using git
2. Host package source on Debian's code forge Salsa
3. Run Salsa CI at least once before every upload to ensure minimal level of quality
4. Allow Merge Requests to be submitted
5. Allow changes to be reviewed before uploads to Debian

See commit for details.