add configuration of gbp

debian/gbp.conf

 [DEFAULT]
-debian-branch = debian/bullseye
-upstream-branch = upstream/bullseye
-debian-tag = debian/bullseye/%(version)s
-upstream-tag = upstream/bullseye/%(version)s
+debian-branch = debian/bookworm
+upstream-branch = upstream/bookworm
+debian-tag = debian/bookworm/%(version)s
+upstream-tag = upstream/bookworm/%(version)s
 
 [buildpackage]
-git-debian-branch = debian/bullseye
-git-debian-tag = debian/bullseye/%(version)s
-git-upstream-tag = upstream/bullseye/%(version)s
+git-debian-branch = debian/bookworm
+git-debian-tag = debian/bookworm/%(version)s
+git-upstream-tag = upstream/bookworm/%(version)s
 
 [import-orig]
 pristine-tar = True