Clarify that app icon must be png or svg

Author: djbpitt

src/main/xar-resources/data/repo/repo.xml

@@ -96,10 +96,10 @@
         </variablelist>
         <para>For library packages <literal>repo.xml</literal> is optional. However, we recommend to
             always provide it for better tool integration.</para>
-        <para>The following is not mentioned in the EXPath spec, but if an image resource with a
-            name that begins with the string <literal>icon</literal> is found in the root directory
-            of an app, the eXist-db dashboard will display that user-supplied image instead of the
-            default eXist-db blue dotted <literal>X</literal>.</para>
+        <para>The following is not mentioned in the EXPath spec, but if an image resource with the
+            filename <literal>icon.png</literal> or <literal>icon.svg</literal> is found in the root
+            directory of an app, the eXist-db dashboard will display that user-supplied image
+            instead of the default eXist-db blue dotted <literal>X</literal>.</para>
 
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