Switch to side-by-side view

--- a/website/doc.html
+++ b/website/doc.html
@@ -46,6 +46,10 @@
       <h1>Other documentation</h1>
 
       <ul>
+        <li><a href="recoll_XMP/index.html">Indexing PDF
+            XMP-metadata</a>: a nice exemple of customizing a Recoll
+            configuration and the PDF filter to use additional
+            metadata.</li>
       <li><a href="perfs.html">Index size and indexing performance
 	  data.</a></li>
       <li><a href="custom.html">Result list format samples.</a></li>