MediaWiki:Common.js

/* Any JavaScript here will be loaded for all users on every page load. */

 var ul = document.querySelector("#p-namespaces ul");//finding the list
     var newLi = document.createElement("li");// creating a list item
     newLi.innerHTML = '<span style="font-weight:bold !important"><a href="https://www.sindenshop.com/" title="Buy Sinden Products">Sinden Shop</a></span>';
 
     ul.appendChild(newLi);//adding list item to list
     var newLi2 = document.createElement("li");
 	 newLi2.innerHTML = '<span style="font-weight:bold !important"><a href="/index.php/Sinden_Lightgun:Contribution_rules" title="How to contribute to this wiki">Contributing</a></span>';
 
     ul.appendChild(newLi2);