Dark mode on folding cell?

[wbwxshao]

Hi, Thanks for the amazing library you made! I use the demo app from folding cell, but I found that if the user turns on the dark mode, the folding cell foreground and background view will not adopt the dark mode. It will still be white or the original background color. Meanwhile, the label on the folding cell is white in dark mode. Could you please take a look at this? Thanks in advance