add configuration of gbp

debian/gbp.conf

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