desktop-utils.exlib: extend categories

exlibs/desktop-utils.exlib

@@ -105,6 +105,12 @@ find_desktop_file_category() {
     local subcat=
 
     case ${CATEGORY} in
+        app*) maincat="Utility"
+            case ${CATEGORY##*-} in
+                editors) subcat="TextEditor";;
+                *) ;;
+            esac
+            ;;
         dev*) maincat="Development"
             case ${CATEGORY##*-} in
                 db) subcat="Database";;