Revamp media player UI

Reworks the media player UI for mobile devices. Adds a swipe gesture to open the media player, and reworks the UI to be more... *hip?*

TODO: haven't implemented a "previous song" feature, is that possible?

![image](/uploads/d329da0ea548eed466227ef39f25301f/image.png)

![image](/uploads/7b3cf83204a1df13b5b166d24d0c2a91/image.png)

![image](/uploads/74c641c544a130eb5e692fb1ae733e37/image.png)