docs/header.html: Add link to patchwork

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

docs/header.html

@@ -55,6 +55,7 @@
     <br><a href="/docs.html">Documentation</a>
     <br><a href="/lists.html">Mailing Lists</a>
     <br><a href="http://autobuild.buildroot.org">Autobuilder</a>
+    <br><a href="http://patchwork.buildroot.org">Patchwork</a>
 
     <p><b>Related Sites</b>
     <br><a href="http://busybox.net/">BusyBox</a>