add maintainability badge

gregor-j · gregor-j · commit 984af0b13f46 · 2023-10-10T16:41:26.000+02:00
diff --git a/README.md b/README.md
@@ -1,6 +1,7 @@
 # PHP/SAP interfaces
 
 [![License: MIT][license-mit]](LICENSE)
+[![Maintainability](https://api.codeclimate.com/v1/badges/743e9c53ed08b8455f50/maintainability)](https://codeclimate.com/github/php-sap/interfaces/maintainability)
 
 This repository defines interfaces for implementing the [PHP/SAP][phpsap] API.
 
