add gitlab-ci file to build and publish html page

.gitlab-ci.yml

+
+pages:
+  stage: deploy
+  image: registry-gitlab.pasteur.fr/hub/courses/sphinx-env/sphinx:1.4.1
+  script:
+    - make html
+    - mv build/html/ public/
+  artifacts:
+    paths:
+      - public
+  only:
+    - master
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