Doc: Added the missing screenshot image

Change-Id: Ifcef698bd735b7fe7e5f4a92984be07a01f283fb
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>

examples/multimediawidgets/player/doc/src/player.qdoc

@@ -31,6 +31,8 @@
     \ingroup multimedia_examples
     \brief Playing audio and video.
 
+    \image mediaplayerex.jpg
+
     \e{Media Player} demonstrates a simple multimedia player that can play
     audio and or video files using various codecs.