Update site-design-overview.md

Update timestamp

Author: a1mery

docs/declarative-customization/site-design-overview.md

@@ -1,7 +1,7 @@
 ---
 title: SharePoint site design and site script overview
 description: Use SharePoint site scripts and site designs to provide custom configurations to apply when new sites are created.
-ms.date: 12/19/2018
+ms.date: 03/24/2020
 localization_priority: Priority
 ---