Add precommit to readme.

README.md

@@ -5,6 +5,7 @@ A discovery service for matching people to the libraries that serve them.
 [![Test Library Registry & Build Docker Image](https://github.com/ThePalaceProject/library-registry/actions/workflows/test-build.yml/badge.svg)](https://github.com/ThePalaceProject/library-registry/actions/workflows/test-build.yml)
 [![Code style: black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/psf/black)
 [![Imports: isort](https://img.shields.io/badge/%20imports-isort-%231674b1?style=flat&labelColor=ef8336)](https://pycqa.github.io/isort/)
+[![pre-commit](https://img.shields.io/badge/pre--commit-enabled-brightgreen?logo=pre-commit&logoColor=white)](https://github.com/pre-commit/pre-commit)
 ![Python: 3.6,3.7,3.8,3.9](https://img.shields.io/badge/Python-3.6%20%7C%203.7%20%7C%203.8%20%7C%203.9-blue)
 
 This is a [LYRASIS](http://lyrasis.org)-maintained fork of the NYPL