Dear jam maintainers,

not placing the Debian packaging files under `debian/` breaks most
standard Debian tools, for example `dch`, `wrap-and-sort`, `gbp` and
Salsa CI.

The MR available at

https://salsa.debian.org/debian/jam/-/merge_requests/1

moves the packaging into the `debian/` directory and marks the Git
repository as an "overlay" (i.e. a repository that does not contain the
upstream sources).

Regards,