Function add_font_from_file 

pub fn add_font_from_file(
    identifier: impl AsRef<str>,
    file: impl AsRef<Path>,
    font_size: f32,
    config: Option<&ImFontConfig>,
    callback: RawFontReceive,
) -> Revertible<impl Fn() + Send + Sync + 'static>

Adds a font from a file path and sends updates to the callback.