Add link to newly available documentation for the ClusterClass blog

Author: fabriziopandini

content/en/blog/_posts/2021-10-08-clusterclass-and-managed-topologies.md

@@ -139,4 +139,4 @@ Stay tuned for what comes next, and if you have any questions, comments or sugge
 * Join the SIG Cluster Lifecycle [Google Group](https://groups.google.com/g/kubernetes-sig-cluster-lifecycle) to receive calendar invites and gain access to documents
 * Join our [Zoom meeting](https://zoom.us/j/861487554), every Wednesday at 10:00 Pacific Time
 * Check out the [ClusterClass quick-start](https://cluster-api.sigs.k8s.io/user/quick-start.html) for the Docker provider (CAPD) in the Cluster API book.
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+* _UPDATE_: Check out the [ClusterClass experimental feature](https://cluster-api.sigs.k8s.io/tasks/experimental-features/cluster-class/index.html) documentation in the Cluster API book.