added: grid_layout to readme index

Author: nisrulz

README.md

@@ -30,6 +30,8 @@ Lookup Links: [[Setup Flutter](https://flutter.io/setup/)] [[Widgets Catalog](ht
 1. [Enable Splash Screen](/enabling_splash_screen) [![download](img/ic_download.png)](https://kinolien.github.com/gitzip/?download=https://github.com/nisrulz/flutter-examples/tree/master/enabling_splash_screen)
 1. [Using Listview](/using_listview) [![download](img/ic_download.png)](https://kinolien.github.com/gitzip/?download=https://github.com/nisrulz/flutter-examples/tree/master/using_listview)
 1. [Using SnackBar](/using_snackbar) [![download](img/ic_download.png)](https://kinolien.github.com/gitzip/?download=https://github.com/nisrulz/flutter-examples/tree/master/using_snackbar)
+1. [Grid Layout](/grid_layout) [![download](img/ic_download.png)](https://kinolien.github.com/gitzip/?download=https://github.com/nisrulz/flutter-examples/tree/master/grid_layout)
+
 
 ### Complete apps with multiple features