Add GitHub Action to lint Python code

[Ruff](https://beta.ruff.rs/) supports [over 500 lint rules](https://beta.ruff.rs/docs/rules) including bandit, isort, pylint, pyupgrade, and flake8 plus its plugins, and is written in Rust for speed.

The `ruff` Action uses minimal steps to run in ~10 seconds, rapidly providing intuitive GitHub Annotations to contributors.

![image](https://user-images.githubusercontent.com/3709715/223758136-afc386d2-70aa-4eff-953a-2c2d82ceea23.png)

.github/workflows/ci.yml

@@ -28,3 +28,10 @@ jobs:
         python-version: ${{ matrix.python-version }}
     - name: Test
       run: python -m unittest discover
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    - run: pip install --user ruff
+    - run: ruff --format=github --ignore=E40,E7,F40,F821,F841
+                --line-length=213 --target-version=py37 .