added allowvr to example iframe (#9769)

examples/index.html

@@ -250,7 +250,7 @@
 			</div>
 			<div id="content"></div>
 		</div>
-		<iframe id="viewer" name="viewer" allowfullscreen onmousewheel=""></iframe>
+		<iframe id="viewer" name="viewer" allowfullscreen allowvr onmousewheel=""></iframe>
 
 		<script src="files.js"></script>