add video and iframe backgrounds to readme

README.md

@@ -385,7 +385,7 @@ Reveal.addEventListener( 'somestate', function() {
 
 ### Slide Backgrounds
 
-Slides are contained within a limited portion of the screen by default to allow them to fit any display and scale uniformly. You can apply full page background colors or images by applying a ```data-background``` attribute to your ```<section>``` elements. Below are a few examples.
+Slides are contained within a limited portion of the screen by default to allow them to fit any display and scale uniformly. You can apply full page backgrounds outside of the slide area by adding a ```data-background``` attribute to your ```<section>``` elements. Four different types of backgrounds are supported: color, image, video and iframe. Below are a few examples.
 
 ```html
 <section data-background="#ff0000">
@@ -397,6 +397,12 @@ Slides are contained within a limited portion of the screen by default to allow
 <section data-background="http://example.com/image.png" data-background-size="100px" data-background-repeat="repeat">
 	<h2>This background image will be sized to 100px and repeated.</h2>
 </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">
+	<h2>Video. Multiple sources can be defined using a comma separated list.</h2>
+</section>
+<section data-background-iframe="https://slides.com">
+	<h2>Embeds a web page as a background. Note that the page won't be interactive.</h2>
+</section>
 ```
 
 Backgrounds transition using a fade animation by default. This can be changed to a linear sliding transition by passing ```backgroundTransition: 'slide'``` to the ```Reveal.initialize()``` call. Alternatively you can set ```data-background-transition``` on any section with a background to override that specific transition.