Add a hint about closing the shop #530

SHOP: Tell player how to "close shop" either by pressing the button or "B." Player kept the shop window open for almsot 20 minutes without knowing how to close it since you can still techincally play through the game with the window open.

While the shop's open, show a panel in the middle of the screen that explains that you can close the shop by clicking again on the gold button, or the key-bound key for toggling shop.