add .gitlab-ci.yml

.gitlab-ci.yml

+# This file is a template, and might need editing before it works on your project.
+# Full project: https://gitlab.com/pages/plain-html
+
+pages:
+  stage: deploy
+  image: lbmc/pandoc:2.11
+  script:
+    - mkdir -p public/img
+    - make
+    - cp img/* public/img/
+  artifacts:
+    paths:
+      - public
+  rules:
+    - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH