added gradient to using_gradient example

using_gradient/lib/main.dart

@@ -13,12 +13,20 @@ void main() {
           ),
           // Body
           body: new Container(
-            // Center the content
-            child: new Center(
-              // Add Text
-              child: new Text(
-                "Hello World!",
+              // Center the content
+              child: new Center(
+                // Add Text
+                child: new Text(
+                  "Hello World!",
+                ),
               ),
-            ),
-          ))));
+              decoration: new BoxDecoration(
+                // Add Gradient
+                gradient: new LinearGradient(
+                    colors: [Colors.lightBlueAccent, Colors.blueAccent],
+                    begin: const FractionalOffset(0.0, 0.0),
+                    end: const FractionalOffset(0.6, 0.0),
+                    stops: [0.0, 0.6],
+                    tileMode: TileMode.clamp),
+              )))));
 }