Add rest api device templates

Author: v-krishnag

articles/iot-central/TOC.yml

@@ -218,6 +218,8 @@
           href: core/howto-authorize-rest-api.md
         - name: Manage users and roles
           href: core/howto-manage-users-roles-with-rest-api.md
+        - name: Device templates
+          href: core/howto-add-device-templates-with-rest-api.md
         - name: Control devices
           href: core/howto-control-devices-with-rest-api.md
         - name: Manage jobs