Merge pull request select2#3006 from WouterSioen/patch-1

Add rel=stylesheet to the cdn link.

Closes select2#3020.

Author: kevin-brown

docs/index.html

@@ -71,7 +71,7 @@ <h3>
         section of your HTML.
 
 <pre class="code">
-&lt;link href="//cdnjs.cloudflare.com/ajax/libs/select2/4.0.0-beta.3/css/select2.min.css" /&gt;
+&lt;link href="//cdnjs.cloudflare.com/ajax/libs/select2/4.0.0-beta.3/css/select2.min.css" rel="stylesheet" /&gt;
 &lt;script src="//cdnjs.cloudflare.com/ajax/libs/select2/4.0.0-beta.3/js/select2.min.js"&gt;&lt;/script&gt;
 </pre>
 
@@ -118,7 +118,7 @@ <h3>
         section of your HTML.
 
 <pre class="code">
-&lt;link href="path/to/select2.min.css" /&gt;
+&lt;link href="path/to/select2.min.css" rel="stylesheet" /&gt;
 &lt;script src="path/to/select2.min.js"&gt;&lt;/script&gt;
 </pre>
       </li>