Added option for javdb to choose folder image

[makeran218]

Expected Behavior

Add folder image from the javdb thumbnail. eg. for this url https://javdb.com/v/6wYRD the cover image is https://jdbimgs.com/covers/6w/6wYRD.jpg but you can get the thumbnail from this https://jdbimgs.com/thumbs/6w/6wYRD.jpg

Current Behavior

Right now for folder image is coming from cropped cover/poster/fanart image