Support for multiple background images
Support for multiple background images

This commit would give the ability to lozad.js to support multiple background images as in
<div style="background: url( 'path/to/main/image' ), url( 'path/to/fallback/image' );"></div>

Initialization will be not so different from existing method, simply add another valid url or multiple ones separated by commas:
<div class="lozad" data-background-image:"path/to/main/image,path/to/fallback/image"></div>

Then, lozad will split the data attribute by comma and join back again to match the css syntax.

This commit is backward compatible; that is, it won't break existing code(s of users of lozad.js).

ApoorvSaxena/lozad.js