Add online example

Author: gonuit

README.md

@@ -103,7 +103,12 @@ CustomRefreshIndicator(
 The best way to understand how the _CustomRefreshIndicator_ widget changes its controller data is to see the example 😉. An example is available in the example application.
 
 <div align="center">
-  <img width="300px" src="readme/controller_data.gif" />
+  <a href="https://custom-refresh-indicator.klyta.it/#/presentation" target="_blank">
+    <img width="300px" src="readme/controller_data.gif" />
+  </a>
+  <p>
+    <a href="https://custom-refresh-indicator.klyta.it/#/presentation" target="_blank">Online example</a>
+  </p>
 <div>
 
 | state        | value   | value description                                                                                       | Description                                                                                                                                                                                                                              |