Doc: Add info about modifying properties for states

Update screenshots.

Change-Id: I6be8a9a844f6c822650fa817756987a43abbd993
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

doc/src/qtquick/qtquick-screens.qdoc

@@ -327,7 +327,7 @@
     example, you can use states to create two screens.
 
     To add states, click the empty slot in the \uicontrol States pane. Then modify the
-    new state in the \uicontrol {Form Editor}.
+    new state in the \uicontrol {Form Editor} or the \uicontrol Properties pane.
 
     \image qmldesigner-states.png "States pane"