add mypy to ci

.github/workflows/python.yml

@@ -37,13 +37,20 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          pip install setuptools wheel pytest
+          pip install setuptools wheel pytest mypy
 
       - name: Build wheel
         working-directory: ./photon-lib/py
         run: |
           python setup.py sdist bdist_wheel
 
+      - name: Run mypy type checking
+        uses: liskin/gh-problem-matcher-wrap@v3
+        with:
+          linters: mypy
+          working-directory: ./photon-lib/py
+          run: mypy --show-column-numbers --exclude=build .
+
       - name: Run Unit Tests
         working-directory: ./photon-lib/py
         run: |