include background video example in default presentation

index.html

@@ -223,6 +223,12 @@ Reveal.addEventListener( 'customevent', function() {
 						<h2>Tiled Backgrounds</h2>
 						<pre><code style="word-wrap: break-word;">&lt;section data-background="image.png" data-background-repeat="repeat" data-background-size="100px"&gt;</code></pre>
 					</section>
+					<section data-background-video="https://s3.amazonaws.com/static.slid.es/site/homepage/v1/homepage-video-editor.mp4,https://s3.amazonaws.com/static.slid.es/site/homepage/v1/homepage-video-editor.webm" data-background-color="#000000">
+						<div style="background-color: rgba(0, 0, 0, 0.9); color: #fff; padding: 20px;">
+							<h2>Video Backgrounds</h2>
+							<pre><code style="word-wrap: break-word;">&lt;section data-background-video="http://example.com/video.mp4,http://example.com/video.webm" data-background-color="#000000"&gt;</code></pre>
+						</div>
+					</section>
 				</section>
 
 				<section data-transition="slide" data-background="#4d7e65" data-background-transition="zoom">