Added lwc relation example

Change-Id: I5ece17297a39ceff815e648d189ddbf3110371b7
diff --git a/dev/demo/relations.html b/dev/demo/relations.html
index fc4ce98..7ef6687 100644
--- a/dev/demo/relations.html
+++ b/dev/demo/relations.html
@@ -16,6 +16,7 @@
             <div class="matchtree">
               <div id="treeRel"></div>
               <div id="treeRel2"></div>
+              <div id="treeRel3"></div>
               <div id="treeHier"></div>
             </div>
           </div>