Update metainfo-desktopapp.xml to better explain desktop applications.

For [this thread](ximion#646 (comment)).

docs/xml/metainfo-desktopapp.xml

@@ -10,7 +10,8 @@
 	<section id="spec-appdata-introduction">
 		<title>Introduction</title>
 		<para>
-			A desktop application is an application which has a graphical user interface and is commonly used with mouse and keyboard. It also ships a Freedesktop
+			A desktop application is a software package which includes a graphical user interface as its primary method of interaction and is designed to be used with mouse and keyboard,
+			irrespective of whether it also supports different invocation target sizes for alternative methods of input, like capacitive touch devices. Its package must include a Freedesktop
 			<filename>.desktop</filename> file to be visible in application menus.
 		</para>
 		<para>