Update README.md

README.md

@@ -2,6 +2,7 @@
 
 [![MIT License](https://img.shields.io/badge/license-MIT-green.svg)](https://github.com/LeetCode-in-Php/LeetCode-in-Php/blob/main/LICENSE)
 [![PHP Composer](https://github.com/LeetCode-in-Php/LeetCode-in-Php/actions/workflows/php.yml/badge.svg)](https://github.com/LeetCode-in-Php/LeetCode-in-Php/actions/workflows/php.yml)
+[![Maintainability Rating](https://sonarcloud.io/api/project_badges/measure?project=LeetCode-in-Php_LeetCode-in-Php&metric=sqale_rating)](https://sonarcloud.io/summary/new_code?id=LeetCode-in-Php_LeetCode-in-Php)
 [![](https://img.shields.io/github/stars/LeetCode-in-Php/LeetCode-in-Php?style=flat-square)](https://github.com/LeetCode-in-Php/LeetCode-in-Php)
 [![](https://img.shields.io/github/forks/LeetCode-in-Php/LeetCode-in-Php?style=flat-square)](https://github.com/LeetCode-in-Php/LeetCode-in-Php/fork)