Added SheetDraggingBar to MiniPlayer

[Integraluminium]

Hello everyone,

Thank you again for this wonderful app. I believe it would be beneficial to add the Draggingbar to the MiniPlayer as a visual indication for users to show that te menu is expandable. In order to adjust the new MiniPlayer to the new height, I modified the variables and extracted the individual heights into local variables. I think the code is now more easily understandable. I hope this code is still managable despite the large refactoring.

Best regards.