enable python formatting with black (#21)

This is the same formatter as LLVM is using.

Author: ftynse

.github/workflows/python_format.yml

@@ -0,0 +1,12 @@
+name: Python-Black
+
+on: [push, pull_request]
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: psf/black@stable
+        with:
+          options: "--check --verbose"