add top-level heading so the page renders correctly (#24491)

Add opening paragraph; update description

website/content/docs/operations/federation/index.mdx

@@ -1,9 +1,16 @@
 ---
 layout: docs
 page_title: Federated cluster operations
-description: Information on running Nomad federated clusters.
+description: |-
+  Operational considerations for running Nomad multi-region federated clusters as well as instructions for migrating the authoritative region to a federated region.
 ---
 
+# Federated cluster operations
+
+This page lists operational considerations for running multi-region federated
+clusters as well as instructions for migrating the authoritative region to a
+federated region.
+
 ## Operational considerations
 
 When operating multi-region federated Nomad clusters, consider the following: