added another demo_gif for horizontal mode in using_stepper example

Author: nisrulz

using_stepper/README.md

@@ -4,7 +4,8 @@ A material stepper widget that displays progress through a sequence of steps. St
 
 Read [[Documentation](https://docs.flutter.io/flutter/material/Stepper-class.html)] [[Material Design Spec](https://material.io/guidelines/components/steppers.html)]
 
-<img src="demo_img.gif" height="600em" />
+<img src="demo_img.gif" height="600em" /> <img src="demo_img_2.gif" height="600em" />
+
 
 ## Getting Started
 

using_stepper/demo_img_2.gif

@@ -51,6 +51,8 @@ class MyHomeState extends State<MyHome> {
         // List the steps you would like to have
         steps: my_steps,
         // Define the type of Stepper style
+        // StepperType.horizontal :  Horizontal Style
+        // StepperType.vertical   :  Vertical Style
         type: StepperType.vertical,
         // Know the step that is tapped
         onStepTapped: (step) {