Function make_previewer 

pub fn make_previewer<T: SSS, S: Selection + 'static>(
    mm: &mut Matchmaker<T, S>,
    previewer_config: PreviewerConfig,
    formatter: AttachmentFormatter<T, S>,
    help_str: Text<'static>,
) -> Previewer

Causes the program to display a preview of the active result. The Previewer can be connected to Matchmaker using PickOptions::previewer