Change TOC to include Arc-K8 security book

Author: richardtaylorrt

AKS-Arc/TOC.yml

@@ -42,6 +42,21 @@
       items:
       - name: Pricing details
         href: https://azure.microsoft.com/pricing/details/azure-stack/aks-hci/
+    - name: Security book - recommendations and best practices
+      items:
+      - name: Introduction and overview
+        href: /azure/azure-arc/kubernetes/conceptual-security-book.md
+        displayName: security, best practices, recommendations
+      - name: Securing your platform
+        href: /azure/azure-arc/kubernetes/conceptual-securing-your-platform.md
+      - name: Securing your workloads
+        href: /azure/azure-arc/kubernetes/conceptual-securing-your-workloads.md
+      - name: Securing your operations
+        href: /azure/azure-arc/kubernetes/conceptual-securing-your-operations.md
+      - name: Securing your data
+        href: /azure/azure-arc/kubernetes/conceptual-securing-your-data.md
+      - name: Securing your network
+        href: /azure/azure-arc/kubernetes/conceptual-securing-your-network.md
   - name: Quickstarts
     items:
     - name: Jumpstart HCIBox (external link)