Add build status

Author: Vectorial1024

README.md

@@ -3,6 +3,8 @@
 ![Packagist Version](https://img.shields.io/packagist/v/vectorial1024/open-location-code-php?style=plastic)
 ![Packagist Downloads](https://img.shields.io/packagist/dm/vectorial1024/open-location-code-php?style=plastic)
 ![PHP Dependency Version](https://img.shields.io/packagist/dependency-v/vectorial1024/open-location-code-php/php?style=plastic&label=PHP)
+![GitHub Actions Workflow Status](https://img.shields.io/github/actions/workflow/status/Vectorial1024/open-location-code-php/php.yml?style=plastic)
+
 
 This is a modern PHP port of the `google/open-location-code` repository. Please visit https://github.com/google/open-location-code for discussion and up-to-date information about **Open Location Code ("OLC", aka "Plus Code")** itself. This repository only concerns the PHP implementation.