Gets a type of the user-selected file.
value = $au.uploader('uploaderID').files().get(index).type();
The type of this file.
Do not confuse this property with format. The file type returned by this property is retrieved from system (determined via the file extension).
This is the same string which is displayed in the Type column of the
Details view. At the same time, file format is determined with
Image Uploader by analyzing file content (rather than the file extension).