GitHub Action to lint Python code (#1025)

* 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 ~5 seconds__, rapidly providing intuitive GitHub Annotations to contributors.

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

* ruff --target-version=py39

.github/workflows/tests.yml

@@ -3,6 +3,13 @@ name: Tests
 on: [push, pull_request]
 
 jobs:
+  ruff:  # https://beta.ruff.rs
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    - run: pip install --user ruff
+    - run: ruff --format=github --line-length=7228 --target-version=py39
+                --ignore=E402,E712,E721,E722,E741,F401,F403,F405,F541,F601,F811,F821,F822,F841 .
   build:
     runs-on: ${{ matrix.os }}
     if: "!contains(github.event.head_commit.message, '[skip ci]')"