add type attribute to atom feed <link> tag

(for /yacysearch.atom)

htroot/yacysearchitem.atom

@@ -1,6 +1,6 @@
 #(content)#::<entry>
 <title type="html">#[title-xml]#</title>
-<link href="#[link]#" />
+<link href="#[link]#" type="#[mimetype]#" />
 <summary type="html">#[description-xml]#</summary>
 <updated>#[date822]#</updated>
 <dc:publisher><![CDATA[#[publisher]#]]></dc:publisher>

htroot/yacysearchitem.java

@@ -227,6 +227,7 @@ public class yacysearchitem {
             prop.put("content_description", desc);
             prop.putXML("content_description-xml", desc);
             prop.putJSON("content_description-json", desc);
+            prop.put("content_mimetype",result.getNode().mime()); // for atom <link> type attribute
             final HeuristicResult heuristic = theSearch.getHeuristic(result.hash());
             if (heuristic == null) {
                 prop.put("content_heuristic", 0);