CI: added package insallation

.gitlab-ci.yml

@@ -5,3 +5,6 @@ test-job:
     - pip3 install -r requirements.txt  # Install Python dependencies
     - pip3 install pytest               # Install pytest
     - pytest test/                      # Run tests
+    - pip3 install build                # Install build package
+    - python3 -m build                  # Build package
+    - pip3 install .                    # Install package