ci: github action to check python types

.github/workflows/mypy-check.yaml

@@ -0,0 +1,32 @@
+name: Mypy Type Checking
+
+on:
+  push:
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  type-check:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Check out code
+      uses: actions/checkout@v2
+
+    - name: Set up Python
+      uses: actions/setup-python@v2
+      with:
+        python-version: '3.9'
+
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
+
+    - name: Install mypy
+      run: |
+        pip install mypy
+
+    - name: Run mypy
+      run: |
+        mypy project.py git_utils.py --check-untyped-defs