add codeclimate badge

README.md

@@ -2,6 +2,7 @@
 
 [![Latest Version on Packagist][ico-version]][link-packagist]
 [![Test Coverage][ico-coverage]][link-coverage]
+[![Maintainability][ico-maintain]][link-maintain]
 [![Total Downloads][ico-downloads]][link-downloads]
 
 Pheature flags toggle CRUD implementation
@@ -29,3 +30,5 @@ knowledge to the community. For this reason we release all our packages under [B
 [link-downloads]: https://packagist.org/packages/pheature/toggle-crud
 [ico-coverage]: https://codecov.io/gh/pheature-flags/toggle-crud/branch/1.0.x/graph/badge.svg?token=DTQIQUZ106
 [link-coverage]: https://codecov.io/gh/pheature-flags/toggle-crud
+[ico-maintain]: https://api.codeclimate.com/v1/badges/e6d9ef290523229a1a0e/maintainability
+[link-maintain]: https://codeclimate.com/github/pheature-flags/toggle-crud/maintainability