cluster api toc update (#2573)

Signed-off-by: ariamarble <armarble@amazon.com>

_api-reference/cluster-api/cluster-allocation.md

@@ -1,7 +1,9 @@
 ---
 layout: default
 title: Cluster allocation explain
-nav_order: 15
+nav_order: 10
+parent: Cluster APIs
+has_children: false
 ---
 
 # Cluster allocation explain

_api-reference/cluster-api/cluster-awareness.md

@@ -1,7 +1,9 @@
 ---
 layout: default
 title: Cluster routing and awareness
-nav_order: 16
+nav_order: 20
+parent: Cluster APIs
+has_children: false
 ---
 
 # Cluster routing and awareness

_api-reference/cluster-api/cluster-decommission.md

@@ -1,7 +1,9 @@
 ---
 layout: default
 title: Cluster decommission 
-nav_order: 20
+nav_order: 30
+parent: Cluster APIs
+has_children: false
 ---
 
 # Cluster decommission

_api-reference/cluster-api/cluster-health.md

@@ -1,7 +1,9 @@
 ---
 layout: default
 title: Cluster health
-nav_order: 17
+nav_order: 40
+parent: Cluster APIs
+has_children: false
 ---
 
 # Cluster health

_api-reference/cluster-api/cluster-settings.md

@@ -1,7 +1,9 @@
 ---
 layout: default
 title: Cluster settings
-nav_order: 18
+nav_order: 50
+parent: Cluster APIs
+has_children: false
 ---
 
 # Cluster settings

_api-reference/cluster-api/cluster-stats.md

@@ -1,7 +1,9 @@
 ---
 layout: default
 title: Cluster stats
-nav_order: 18
+nav_order: 60
+parent: Cluster APIs
+has_children: false
 ---
 
 # Cluster stats

_api-reference/cluster-api/index.md

@@ -0,0 +1,12 @@
+---
+layout: default
+title: Cluster APIs
+has_children: true
+nav_order: 15
+redirect_from:
+  - /opensearch/api-reference/cluster-api/
+---
+
+# Cluster APIs
+
+The cluster APIs allow you to manage your cluster. You can use them to check cluster health, modify settings, retrieve statistics, and more.