Update README.md with ruff badge

README.md

@@ -13,6 +13,7 @@ A light weight tool for creating summary statistics from dataframes.
 [![Tests](https://github.com/aeturrell/skimpy/workflows/Tests/badge.svg)](https://github.com/aeturrell/skimpy/actions?workflow=Tests)
 [![Codecov](https://codecov.io/gh/aeturrell/skimpy/branch/main/graph/badge.svg)](https://codecov.io/gh/aeturrell/skimpy)
 [![pre-commit](https://img.shields.io/badge/pre--commit-enabled-brightgreen?logo=pre-commit&logoColor=white)](https://github.com/pre-commit/pre-commit)
+[![Ruff](https://img.shields.io/endpoint?url=https://raw.githubusercontent.com/astral-sh/ruff/main/assets/badge/v2.json)](https://github.com/astral-sh/ruff)
 [![Google Colab](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/gist/aeturrell/7bf183c559dc1d15ab7e7aaac39ea0ed/skimpy_demo.ipynb)
 [![Downloads](https://static.pepy.tech/badge/skimpy)](https://pepy.tech/project/skimpy)
 [![Source](https://img.shields.io/badge/source%20code-github-lightgrey?style=for-the-badge)](https://github.com/aeturrell/skimpy)