Add CI badge.

Author: dereuromark

readme.md

@@ -1,5 +1,6 @@
 # File Storage Image Processing
 
+[![CI](https://github.com/php-collective/file-storage-image-processor/actions/workflows/ci.yml/badge.svg?branch=master)](https://github.com/php-collective/file-storage-image-processor/actions/workflows/ci.yml)
 [![Software License](https://img.shields.io/badge/license-MIT-brightgreen.svg?style=flat-square)](LICENSE)
 
 Image Processing for the [File Storage Library](https://github.com/php-collective/file-storage-image-processor).