updated github action

Author: manfred-kaiser

.github/workflows/python-package.yml

@@ -26,8 +26,8 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install flake8 pytest
-        if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
+        pip install flake8 pytest mypy
+        pip install -U .
     - name: Lint with flake8
       run: |
         # stop the build if there are Python syntax errors or undefined names
@@ -37,3 +37,6 @@ jobs:
     - name: Test with pytest
       run: |
         pytest
+    - name: Test with mypy
+      run: |
+        mypy --strict sifter