Adding new test

.gitlab-ci.yml

 stages:       
    # List of stages for jobs, and their order of execution
   - build_branch # builds if the image does not exist
-  - build_main  # builds when the merge request is made into main
+  - check_image_tag # Check whether there are any vulnerabilities in the image
   - branch_scan # Check whether the image is already existing or not for the tag
+  - build_main  # builds when the merge request is made into main
   - build_tag  # builds when the tag is pushed
   - test_main # tests when the merge request is made into main
   - test_latest # tests when the image with tag latest is pushed