Add link to the readme and image to qml tutorial3

Signed-off-by: Juraj Oravec <jurajoravec@mailo.com>

qml/README.md

@@ -2,3 +2,4 @@
 
 1. [Introduction](articles/1.Introduction.md)
 2. [Basic Extension](articles/2.Basic_extension.md) - [Extension](extensions/qml_tutorial_2/)
+3. [Adding a button to the toolbar](articles/3.Adding_a_button_to_the_toolbar.md) - [Extension](extensions/qml_tutorial_3/)

qml/articles/3.Adding_a_button_to_the_toolbar.md

@@ -67,10 +67,13 @@ detection and maybe some other things as well, I did not try that
 though.
 
 
-## Code
+## Example
 The example code will add a button to main toolbar and statusbar. When
 user clicks on the button the small white rectangle will show up and the
 number displayed on the badge will increase.
 
+![Toolbar button with badge and empty popup](../images/tutorial3/toolbar_button_with_badge_and_popup.png)
+
+### Code
 The code for this example can be found at
 [extensions/qml_tutorial_3](../extensions/qml_tutorial_3)