Add appropriate kudos markers to appdata

As requested by upstream, we're adding all manually-assigned kudos that
apply to Meld. Unless the list of manually-specified kudos changes,
this list is unlikely to change, since we have no reason to use some of
the other kudo integration markers (e.g., notifications).

Author: kaiw

data/meld.appdata.xml.in

@@ -16,6 +16,13 @@
   merge conflicts slightly less painful.
   </_p>
  </description>
+ <kudos>
+  <kudo>AppMenu</kudo>
+  <kudo>HiDpiIcon</kudo>
+  <kudo>HighContrast</kudo>
+  <kudo>ModernToolkit</kudo>
+  <kudo>UserDocs</kudo>
+ </kudos>
  <screenshots>
   <screenshot type="default" width="992" height="759">http://meldmerge.org/images/meld-filediff-full.png</screenshot>
   <screenshot width="655" height="532">http://meldmerge.org/images/meld-dircomp-full.png</screenshot>