Note that App Service Health Check is in Preview

Co-authored-by: Tom Harvey <tombuildsstuff@users.noreply.github.com>

website/docs/r/app_service.html.markdown

@@ -189,6 +189,8 @@ A `site_config` block supports the following:
 
 * `health_check_path` - (Optional) The health check path to be pinged by App Service. [For more information - please see the corresponding Kudu Wiki page](https://github.com/projectkudu/kudu/wiki/Health-Check-(Preview)).
 
+~> **Note:** This functionality is in Preview and is subject to changes (including breaking changes) on Azure's end
+
 * `http2_enabled` - (Optional) Is HTTP2 Enabled on this App Service? Defaults to `false`.
 
 * `ip_restriction` - (Optional) A [List of objects](/docs/configuration/attr-as-blocks.html) representing ip restrictions as defined below.