Bandcamp Cart Upgrade

Quality of life improvements to the bandcamp cart

Adds a couple of quality of life improvements for digging on bandcamp. The extension adds a player to the bottom bar, which can play your cart or a full artist / label discography. Also adds play buttons to the cart / release info on the page to skip to that release in the player immediately - When playing the cart playlist there is a button to remove the track that's playing from your cart (behind a confirmation popup) - When playing the label playlist, there is a button to add the track or full release that's playing to your cart - Playing the full artist / label discography is only available on label / artist pages - Being able to check out a part of your cart instead of the full cart