Update .gitlab-ci.yml file

Auto Doxygen deployment

.gitlab-ci.yml

+image: alpine
+
+pages:
+  script:
+  - apk update && apk add doxygen
+  - doxygen Doxygen/Doxyfile
+  - mv Doxygen/documentation/html/ public/
+  artifacts:
+    paths:
+    - public
+  only:
+  - master