feat: initial ci/cd pipeline

.gitlab-ci.yml

+image: git-r3lab.uni.lu:4567/r3/docker/latex:latest
+
+stages:
+  - build
+
+build:pages:
+  stage: build
+  artifacts:
+    expire_in: 1 day
+    paths:
+      - build
+  before_script:
+    - apt install make
+  script:
+    - mkdir -p build
+    - make
+    - cp *.pdf build