Update CONTRIBUTING.md

PokhodenkoSA · PokhodenkoSA · commit c9ab60a16256 · 2020-10-15T11:24:20.000+03:00
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
@@ -1 +1,10 @@
-Coming soon
+# Python code style
+
+## black
+
+We use [black](https://black.readthedocs.io/en/stable/) code formatter.
+
+- Revision: `20.8b1` or branch `stable`.
+- See configuration in `pyproject.toml`.
+
+Run before each commit: `black .`
