Update README.md

Author: jingningzhang1

README.md

@@ -18,6 +18,8 @@ Built on top of Plotly.js, React and Flask, Dash ties modern UI elements like dr
 
 - [Dash Docs on Heroku](https://dash-docs.herokuapp.com/) (for corporate network that cannot access plotly.com)
 
+- [Open-Source App Gallery] (https://dash-gallery.plotly.host/Portal/) With sample code and templates!
+
 ### App Samples
 
 | App | Description |