Added link to SharePoint toolkit. (SharePoint#886)

* Initialize open publishing repository: https://github.com/SharePoint/sp-dev-docs of branch live

* Initialize open publishing repository: https://github.com/SharePoint/sp-dev-docs of branch live

* Update grid-and-responsive-design.md

Author: Lauragra

docs/design/grid-and-responsive-design.md

@@ -147,6 +147,8 @@ The responsive grid for both team sites and communication sites adjusts when goi
 | 1600         | Web 1600x900            | XX-Large   | 12      | 32     | 3                       |
 | 1920         | Web 1920x1080           | XXX-Large  | 12      | 32     | 3                       |
 
+## See also
 
+- [Design toolkit and assets](https://developer.microsoft.com/en-us/fabric#/resources)