Add GitHub Actions CI workflow

.github/workflows/python-ci.yml

@@ -0,0 +1,21 @@
+name: Python CI
+
+on: [push, pull_request]
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Set up Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.10'
+
+      - name: Install flake8
+        run: pip install flake8
+
+      - name: Run flake8
+        run: flake8 .