added gitlab CI config file

.gitlab-ci.yml

+image: docker:latest
+
+variables:
+    DOCKER_TLS_CERTDIR: "/certs"
+    BRANCH_IMAGE: $CI_REGISTRY/foodinformatics/msx-tool:$CI_COMMIT_REF_NAME
+
+services:
+    - docker:dind
+
+stages:
+    - build
+
+build:
+    stage: build
+    script:
+        - docker login -u $CI_REGISTRY_USER -p $CI_REGISTRY_PASSWORD $CI_REGISTRY
+        - docker build -t $BRANCH_IMAGE .
+        - docker push $BRANCH_IMAGE