Add type checker (#3116)

.github/workflows/misc_0.yml

@@ -152,3 +152,21 @@ jobs:
 
       - name: Run tests
         run: tox -e ruff
+
+  typecheck:
+    name: typecheck
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repo @ SHA - ${{ github.sha }}
+        uses: actions/checkout@v4
+
+      - name: Set up Python 3.11
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+
+      - name: Install tox
+        run: pip install tox
+
+      - name: Run tests
+        run: tox -e typecheck