Add config env requirement

doc/ci/environments.md

@@ -49,6 +49,7 @@ Configuring environments involves:
 
 1. Understanding how [pipelines](pipelines.md) work.
 1. Defining environments in your project's [`.gitlab-ci.yml`](yaml/README.md) file.
+1. Creating a job configured to deploy your application. For example, a deploy job configured with [`environment`](yaml/README.md#environment) to deploy your application to a [Kubernetes cluster](../user/project/clusters/index.md).
 
 The rest of this section illustrates how to configure environments and deployments using
 an example scenario. It assumes you have already: