Add CI build

.gitlab-ci.yml

+stages:
+  - build
+
+variables:
+  GIT_SUBMODULE_STRATEGY: normal
+
+build:
+  stage: build
+  image: registry.gitlab.com/islandoftex/images/texlive:latest
+  before_script:
+    - echo $CI_JOB_ID
+    - echo BLD_JOB_ID=$CI_JOB_ID >> build.env
+  script:
+    - latexmk
+  after_script:
+    - cat main.log
+  artifacts:
+    paths:
+      - main.pdf
+    reports:
+      # To ensure we've access to this file in the release stage
+      dotenv: build.env