update thumbnav.md

Author: janschoenherr

docs/pages/thumbnav.md

@@ -81,7 +81,7 @@ To position the thumbnav on top of an element or the [Slideshow component](slide
     </div>
 
     <div class="uk-position-bottom-center uk-position-small">
-        <ul class="uk-thumbnav">
+        <ul class="uk-slideshow-nav uk-thumbnav">
             <li uk-slideshow-item="0"><a href="#"><img src="images/photo.jpg" width="100" height="67" alt=""></a></li>
             <li uk-slideshow-item="1"><a href="#"><img src="images/dark.jpg" width="100" height="67" alt=""></a></li>
             <li uk-slideshow-item="2"><a href="#"><img src="images/light.jpg" width="100" height="67" alt=""></a></li>