Merge pull request #259993 from hilaryw29/patch-20

Application Health Extension documentation for SI VMs

Author: JamesJBarnett

articles/virtual-machines/TOC.yml

@@ -979,6 +979,8 @@
         href: ./extensions/key-vault-windows.md
     - name: Azure Policy guest configuration
       href: ./extensions/guest-configuration.md
+    - name: Application Health Extension
+      href: ./extensions/health-extension.md
     - name: Custom Script
       items:
       - name: Linux - version 2