update ci for image build

.gitlab-ci.yml

@@ -2,6 +2,7 @@ image: docker:20.10.22
 
 stages:
   - test
+  - build
 
 ##############
 # TEST STAGE #
@@ -22,3 +23,23 @@ test:
   rules:
     - if: '$CI_MERGE_REQUEST_TARGET_BRANCH_NAME == $CI_DEFAULT_BRANCH || $CI_COMMIT_MESSAGE =~ /--check/ || $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH' 
       when: always
+
+###############
+# BUILD STAGE #
+###############
+
+build:
+  stage: build
+  image: docker:20.10.22
+  variables:
+    DOCKER_TLS_CERTDIR: ""
+  services:
+    - docker:dind
+  before_script:
+    - docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY
+  script:
+    - docker build --pull -t "$CI_REGISTRY_IMAGE" .
+    - docker push "$CI_REGISTRY_IMAGE"
+  only:
+    - main
+  when: manual