add link to README for visibility

Author: danielkon96

README.md

@@ -43,6 +43,7 @@ bash main.sh -a easy-auth-demo -c {insert-unique-hostname} -r easy-auth -e email
 
 ## Documentation
 * [Setup Instructions](docs/setup-instructions.md) - step-by-step guide to building a cluster, configuring the ingress controller, and deploying an application protected by EasyAuth
+* [Deploy to an Existing Cluster](docs/deploy-to-existing-cluster.md) - an in-depth guide to deploying EasyAuth to an existing cluster and application
 * [Detailed Architecture](docs/detailed-architecture.md) - an in-depth guide to how EasyAuth works
 * [Calling a Protected API](docs/protecting-an-api.md) - how to authenticate a client application and call an API protected by EasyAuth
 * [Http Headers](docs/headers.md) - Get information about the user that is accessing your application