Add ruff linting

.github/workflows/checks.yaml

@@ -19,3 +19,19 @@ jobs:
         run: |
           python -m pip install pipenv
           pipenv install --skip-lock  # this is what Elastic beanstalk uses
+  lint:
+    name: lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Setup Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: "3.11"
+
+      - name: Install dependencies
+        run: python3 -m pip install ".[dev]"
+
+      - name: Check style
+        run: python3 -m ruff check . && python3 -m ruff format --check .