Add .gitlab-ci.yml

.gitlab-ci.yml

+# This file is a template, and might need editing before it works on your project.
+# Official docker image.
+image: docker:latest
+
+services:
+  - docker:dind
+
+build:
+  stage: build
+  script:
+    - export IMAGE_TAG=$(echo -en $CI_BUILD_REF_NAME | tr -c '[:alnum:]_.-' '-')
+    - docker login -u "gitlab-ci-token" -p "$CI_BUILD_TOKEN" $CI_REGISTRY
+    - docker build --pull -t "$CI_REGISTRY_IMAGE:$IMAGE_TAG" .
+    - docker push "$CI_REGISTRY_IMAGE:$IMAGE_TAG"