Add feature gate StorageNamespaceIndex for v1.32

Author: tengqm

content/en/docs/reference/command-line-tools-reference/feature-gates/StorageNamespaceIndex.md

@@ -0,0 +1,16 @@
+---
+title: StorageNamespaceIndex
+content_type: feature_gate
+
+_build:
+  list: never
+  render: false
+
+stages:
+  - stage: beta 
+    defaultValue: true
+    fromVersion: "1.30"
+---
+Enables a namespace indexer for namespace scoped resources
+in API server cache to accelerate list operations.
+