fix: add types tests to CI

Closes #15

.github/workflows/python-app.yml

@@ -24,14 +24,17 @@ jobs:
       run: |
         apt-get update && apt-get install -y fdisk jq
         python -m pip install --upgrade pip
-        pip install flake8 pytest
+        pip install flake8 pytest mypy
         if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
     - name: Lint with flake8
       run: |
         # stop the build if there are Python syntax errors or undefined names
         flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
         # exit-zero treats all errors as warnings. The GitHub editor is 127 chars wide
         flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
+    - name: Test types with Mypy
+      run: |
+        mypy gpt_image --strict
     - name: Test with pytest
       run: |
         pytest