added new Python versions to the pipeline

.gitlab-ci.yml

@@ -56,6 +56,10 @@ build-job:       # This job runs in the build stage, which runs first.
 
 unit-test-job:   # This job runs in the test stage.
   stage: test
+  parallel: 
+    matrix:
+      - PYTHON_VERSION: ["3.8", "3.9", "3.10"]
+  image: python:${PYTHON_VERSION}
   script:
     - echo "Running unit tests..."
     - pip install pytest