ci: add gitlab ci

.gitlab-ci.yml

+include:
+ - 'https://source.puri.sm/Librem5/librem5-ci/raw/master/librem5-pipeline-definitions.yml'
+
+stages:
+ - package
+ - test-package
+
+variables:
+  L5_DOCKER_IMAGE: pureos/byzantium
+  L5_ADD_SCRATCH_CI: 'false'
+
+package:deb-pureos-byzantium:
+  extends: .l5-build-debian-package
+
+lintian-pureos-byzantium-package:
+  dependencies:
+    - package:deb-pureos-byzantium
+  extends: .l5-lintian-debian-package
+
+