Merge pull request #47505 from guettli/patch-14

Added Cluster API to "Installing Kubernetes"

Author: k8s-ci-robot

content/en/docs/setup/production-environment/tools/_index.md

@@ -9,6 +9,10 @@ For example:
 
 - [kubeadm](/docs/setup/production-environment/tools/kubeadm/)
 
+- [Cluster API](https://cluster-api.sigs.k8s.io/): A Kubernetes sub-project focused on
+  providing declarative APIs and tooling to simplify provisioning, upgrading, and operating
+  multiple Kubernetes clusters.
+  
 - [kops](https://kops.sigs.k8s.io/): An automated cluster provisioning tool.
   For tutorials, best practices, configuration options  and information on
   reaching out to the community, please check the