Update .gitlab-ci.yml

.gitlab-ci.yml

 build_image:
-  image: docker:18.09.7
+  stage: build
+  image: 'docker:18.09.7'
   only:
     - master
   services:
     - 'docker:18.09.7-dind'
+  variables:
+    DOCKERHUB_NAME: clarinpl/$CI_PROJECT_NAME
+  before_script:
+    - ''
   script:
-    - docker build -t clarinpl/editext .
+    - docker build -t $DOCKERHUB_NAME .
     - echo $DOCKER_PASSWORD > pass.txt
     - cat pass.txt | docker login --username $DOCKER_USERNAME --password-stdin
     - rm pass.txt
-    - docker push clarinpl/editext
- 
+    - docker push $DOCKERHUB_NAME
+    - docker login -u $CI_REGISTRY_USER -p $CI_REGISTRY_PASSWORD $CI_REGISTRY
+    - docker image tag $DOCKERHUB_NAME $CI_REGISTRY_IMAGE:$CI_COMMIT_REF_SLUG
+    - docker image tag $DOCKERHUB_NAME $CI_REGISTRY_IMAGE:latest
+    - docker push $CI_REGISTRY_IMAGE
+