Fix search button in rtl languages in Chrome

For some reason without position: relative the search button is hidden
in rtl languages.

lib/tpl/dokuwiki/css/design.css

@@ -205,6 +205,7 @@
     background-position: 5px 0;
     margin-left: 0;
     margin-right: -20px;
+    position: relative;
 }
 
 #dokuwiki__sitetools ul {