gitlab-ci: add a test for bookworm

Signed-off-by: Mattia Rizzolo <mattia@debian.org>

.gitlab-ci.yml

@@ -42,12 +42,16 @@ test buster:
     - master
   image: debian:buster-backports
   variables:
-    ADDITIONAL_PACKAGES: python3-django/buster-backports
+    ADDITIONAL_PACKAGES: python3-django/buster-backports git/buster-backports git-man/buster-backports
 
 tests bullseye:
   <<: *test
   image: debian:bullseye
 
+tests bookworm:
+  <<: *test
+  image: debian:bookworm
+
 test unstable:
   <<: *test
   image: debian:unstable