The FileStyle structure describes the parameters of messages with files
Description of FileStyle parameters:
iconMargin: UIEdgeInsets - file icon indents relative to message edges and file name
imageIcon: UIImage - file icon image
iconSize: CGSize - file icon image size
fontName: UIFont - file name text font
nameMargin: UIEdgeInsets - external indents of the file name text. Indents from the top edge of the message background and the right edge
nameColor: UIColor - the color of the file name text
fontSize: UIFont - file size text font
sizeMargin: UIEdgeInsets - file size text margins. The top indent up to the file name and to the right edge of the message background are taken into account
