Recognise Leif Warland

.. added to contributors page

src/AboutDialog.cpp

@@ -155,6 +155,7 @@ ContributorsPage::ContributorsPage(Context *context) : context(context)
     contributors.append("Keisuke Yamaguchi");
     contributors.append("Keith Reynolds");
     contributors.append("Ken Sallot");
+    contributors.append("Leif Warland");
     contributors.append("Luke NRG");
     contributors.append("Magnus Gille");
     contributors.append("Marc Boudreau");