added spot-node-pool to TOC

Author: MGoedtel

articles/aks/TOC.yml

@@ -289,6 +289,8 @@
               href: create-node-pools.md
             - name: Manage node pools
               href: manage-node-pools.md
+            - name: Add an Azure Spot node pool
+              href: spot-node-pool.md
             - name: Multi-instance GPU Node pool
               href: gpu-multi-instance.md
             - name: Node pool snapshot