Use black to format Python files

Black is a popular Python code formatter. By using it, contributors
don't need to think about the project's styles preferences and avoids
the need for hand-formatting. Instead, let the tool handle it. This can
help smooth the review process.

Updated existing tools to follow the integration docs:
https://black.readthedocs.io/en/stable/guides/using_black_with_other_tools.html

For more details, see the project:
https://github.com/psf/black

.github/workflows/black.yml

@@ -0,0 +1,12 @@
+name: black
+
+on:
+  - push
+  - pull_request
+
+jobs:
+  black:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: psf/black@stable

codespell_lib/__main__.py

@@ -1,4 +1,4 @@
 from ._codespell import _script_main
 
-if __name__ == '__main__':
+if __name__ == "__main__":
     _script_main()