Add a CI file

.gitlab-ci.yml

+image: docker:stable
+
+services:
+  - docker:stable-dind
+
+before_script:
+  - docker login -u gitlab-ci-token -p $CI_JOB_TOKEN $CI_REGISTRY
+
+build:
+  stage: build
+  script:
+    - docker build --tag $CI_REGISTRY_IMAGE:fluentd fluentd/fluent-plugin-loki
+    - docker push $CI_REGISTRY_IMAGE:fluentd
+