Add badge like the rest of em.

Author: chadcarlson

README.md

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 # Platform.sh Config Reader (PHP)
 
+![Quality Assurance](https://github.com/platformsh/config-reader-go/workflows/Quality%20Assurance/badge.svg)
+
 This library provides a streamlined and easy to use way to interact with a Platform.sh environment.  It offers utility methods to access routes and relationships more cleanly than reading the raw environment variables yourself.
 
 This library requires PHP 7.2 or later.