Function gifski::c_api::gifski_add_frame_png_file

#[no_mangle]
pub unsafe extern "C" fn gifski_add_frame_png_file(
    handle: *const GifskiHandle, 
    index: u32, 
    file_path: *const c_char, 
    delay: u16
) -> GifskiError

File path must be valid UTF-8. This function is asynchronous.

Delay is in 1/100ths of a second.

Returns 0 (GIFSKI_OK) on success, and non-0 GIFSKI_* constant on error.