Update design-sharepoint-add-ins.md (SharePoint#2620)

* Update design-sharepoint-add-ins.md

* Updated date

Author: Seiyasu

docs/sp-add-ins/design-sharepoint-add-ins.md

@@ -1,7 +1,7 @@
 ---
 title: Design SharePoint Add-ins
 description: An overview of the design and architecture options available in SharePoint Add-ins, and how to make the right decisions to ease your add-in's development.
-ms.date: 11/02/2017
+ms.date: 09/24/2018
 ms.prod: sharepoint
 ---
 
@@ -61,7 +61,7 @@ Have a solid design for your add-in? Get ready to build your add-in and publish
 -  [Reimagine SharePoint development](http://msdn.microsoft.com/en-US/office/apps/dn133840)
 -  [SharePoint Add-ins](sharepoint-add-ins.md)
 -  [Develop SharePoint Add-ins](develop-sharepoint-add-ins.md)
--  [Blog for add-ins](http://blogs.msdn.com/b/spoffapps)
+-  [Blog for add-ins](https://developer.microsoft.com/en-us/office/blogs/technology/add-ins/)