add gif demo

Author: PeterDaveHello

Demo.gif

@@ -31,6 +31,10 @@ Make echo colorful with easier method. In [bash](https://www.gnu.org/software/ba
 
 ![Screenshot](https://cdn.rawgit.com/PeterDaveHello/ColorEchoForShell/master/Demo.png)
 
+## Demo
+
+![Demo](https://cdn.rawgit.com/PeterDaveHello/ColorEchoForShell/master/Demo.gif)
+
 ## Author
 
 [Peter Dave Hello](https://www.peterdavehello.org/), [@Twitter](https://twitter.com/PeterDaveHello), [@GitHub](https://github.com/PeterDaveHello)