feat(ci): add Black code formatter and enable linting

- Add Black to the pip install command alongside flake8
- Uncomment and update the linting step to use Black for code style checking
- Replace flake8 linting with Black's --check option

This change enhances the CI pipeline by introducing code formatting checks,
ensuring consistent code style across the project.

.github/workflows/test.yml

@@ -30,10 +30,10 @@ jobs:
       run: |
         python -m pip install --upgrade pip
         pip install -r requirements.txt
-        pip install flake8
+        pip install flake8 black
 
-    # - name: Run linting
-    #   run: flake8 .
+    - name: Run linting
+      run: black --check .
 
     - name: Run tests with unittest
       id: run-tests