Added example Fixes #2944 (#3036)

files/en-us/web/html/link_types/preconnect/index.html

@@ -10,6 +10,11 @@
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 <p><span class="seoSummary">The <strong><code>preconnect</code></strong> keyword for the {{HTMLAttrxRef("rel", "link")}} attribute of the {{HTMLElement("link")}} element is a hint to browsers that the user is likely to need resources from the target resource's origin, and therefore the browser can likely improve the user experience by preemptively  initiating a connection to that origin.</span></p>
 
+<pre class="brush: html">&lt;link rel="preconnect" href="https://example.com"&gt;
+</pre>
+
+
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 <h2 id="Specifications">Specifications</h2>
 
 <table class="standard-table">