Bug#1138091: install upstream change log document

[Ben Finney]

Package: systemd
Version: 257.13-1~deb13u1
Severity: minor

Currently, the Debian release of SystemD does not install the upstream
changelog document. This file is part of source releases, as the file
‘./NEWS’.

The recommendation to install the upstream changelog document is specified
in Policy §12.7:

    If there is an upstream changelog available, it may be made available
    as "/usr/share/doc/package/changelog.gz".

The ‘dh_installchangelogs’ packaging rule can make this easy.