fixed: side shadow in the wrong direction
fixed: side shadow in the wrong direction

Sweetymeow/PaperFold-for-iOS,AmitaiB/PaperFold-for-iOS,gank0326/PaperFold,jasperblues/PaperFold-for-iOS,honcheng/PaperFold-for-iOS,AmitaiB/PaperFold-for-iOS,godLoveLucifer/PaperFold-for-iOS,jasperblues/PaperFold-for-iOS,Sweetymeow/PaperFold-for-iOS,gank0326/PaperFold,godLoveLucifer/PaperFold-for-iOS,honcheng/PaperFold-for-iOS