This has been changed/updated in version 1.2.2.
The type of files allowed for upload. This is taken from the file’s mime type. To allow all images, set this option to ‘image/*’. To allow a specific type of image, set this option to ‘image/png’. To allow all files, set this value to false. To accept a set of files with different MIME types, separate each with a pipe “|” character. For a complete list of MIME types, please visit Media Types at iana.org.