docs: add CI badge to README

Author: JeroenSoeters

README.md

@@ -1,5 +1,7 @@
 # AWS Plugin for Formae
 
+[![CI](https://github.com/platform-engineering-labs/formae-plugin-aws/actions/workflows/ci.yml/badge.svg)](https://github.com/platform-engineering-labs/formae-plugin-aws/actions/workflows/ci.yml)
+
 AWS resource plugin for [formae](https://github.com/platform-engineering-labs/formae). This plugin enables Formae to manage AWS resources using the [AWS Cloud Control API](https://docs.aws.amazon.com/cloudcontrolapi/latest/userguide/what-is-cloudcontrolapi.html).
 
 ## Installation