Function run 

pub fn run<I: BufRead>(
    file_name: Option<&str>,
    input: &mut I,
) -> Result<(), Error>

Set up the terminal and run the text editor. If file_name is not None, load the file.

Update the panic hook to restore the terminal on panic.

Errors

Will Return Err if any error occur when registering the window size signal handler, enabling raw mode, or running the editor.