Add mypy to test action

Author: RalfG

.github/workflows/test.yml

@@ -18,19 +18,22 @@ jobs:
         with:
           python-version: "3.10"
 
-      - name: Check formatting with Ruff
+      - name: Lint with Ruff
         uses: astral-sh/ruff-action@v3
         with:
-          args: format --check --diff --exclude docs,tests
+          args: check --exclude docs,tests
 
-      - name: Lint with Ruff
+      - name: Check formatting with Ruff
         uses: astral-sh/ruff-action@v3
         with:
-          args: check --exclude docs,tests
+          args: format --check --diff --exclude docs,tests
 
       - name: Install package and its dependencies
         run: pip install --editable .[dev,idxml]
 
+      - name: Static type checking with mypy
+        run: mypy
+
       - name: Test with pytest and codecov
         run: |
           pytest --cov=psm_utils --cov-report=xml tests/