Recognize Mitja Zupanic

For his contributions with graphical items
and goldencheetah.org website new design.

src/Gui/AboutDialog.cpp

@@ -175,6 +175,7 @@ ContributorsPage::ContributorsPage(Context *context) : context(context)
     contributors.append("Mark Rages");
     contributors.append("Michael Puchowicz");
     contributors.append("Michel Dagenais");
+    contributors.append("Mitja Zupanic");
     contributors.append("Mitsukuni Sato");
     contributors.append("Ned Harding");
     contributors.append("Nicholas Feng");