Readme: Add black Badge

README.md

@@ -4,6 +4,7 @@
 [![PyPI - Version](https://img.shields.io/pypi/v/not-my-board)](https://pypi.org/project/not-my-board/)
 ![Python Version from PEP 621 TOML](https://img.shields.io/python/required-version-toml?tomlFilePath=https%3A%2F%2Fraw.githubusercontent.com%2Fholesch%2Fnot-my-board%2Fmaster%2Fpyproject.toml)
 ![PyPI - Status](https://img.shields.io/pypi/status/not-my-board)
+[![Code style: black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/psf/black)
 
 not-my-board is a tool to manage a pool of embedded hardware setups and to
 schedule and provide access to those setups over a local network. The concept is