Add id argument to embed_media() functions

[mccarthy-m-g]

The HTML5 <audio> tag does not have many options for CSS styling (its appearance is pretty much restricted to the browser defaults for the tag), however, JavaScript can be used to give audio elements a customized appearance. This can be done by adding an id argument to the tag and not specifying any attributes (e.g., <audio id=‘player’>), along with JS code to handle the styling.

Adding this is desirable, as users may want to customize the player’s appearance.