Added TOC for HPA document for better reference. (#7624)

docs/tasks/run-application/horizontal-pod-autoscale-walkthrough.md

@@ -7,6 +7,9 @@ reviewers:
 title: Horizontal Pod Autoscaler Walkthrough
 ---
 
+* TOC
+{:toc}
+
 Horizontal Pod Autoscaler automatically scales the number of pods
 in a replication controller, deployment or replica set based on observed CPU utilization
 (or, with beta support, on some other, application-provided metrics).

docs/tasks/run-application/horizontal-pod-autoscale.md

@@ -6,6 +6,9 @@ reviewers:
 title: Horizontal Pod Autoscaler
 ---
 
+* TOC
+{:toc}
+
 This document describes the current state of the Horizontal Pod Autoscaler in Kubernetes.
 
 ## What is the Horizontal Pod Autoscaler?