Update README.md

README.md

@@ -39,7 +39,7 @@ success%
 
 You should now be able to navigate to `http://<ip of ESP>`. It should look like this:
 
-![Web UI](http://imgur.com/XNNigvL)
+![Web UI](http://imgur.com/XNNigvL.png)
 
 ## REST endpoints