Adding the promote-js embed script

__About promote MDN script__
People can embed this code in their sites and it will scan their site content for keywords such as 'JavaScript' and will link it back to the corresponding page on MDN on that topic.

__Code to embed in sites__

    <!-- Include the below line only if the page doesn't have jQuery included already -->
    <script src="https://code.jquery.com/jquery-2.1.0.min.js"></script>

    <!-- The rest of the lines are required -->
    <script>
        (function(){
            window._promote_mdn_options = {maxlinks: 3}; // Configurable settings
            var e = document.createElement('script'); e.type='text/javascript';
            e.src = document.location.protocol + '//developer.cdn.mozilla.net/media/redesign/js/promote-mdn.js';
            var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(e, s);
        })();
    </script>