Function ghost_encode_with_shadows_quality 

pub fn ghost_encode_with_shadows_quality(
    image_bytes: &[u8],
    message: &str,
    files: &[FileEntry],
    passphrase: &str,
    shadows: &[ShadowLayer],
    si: Option<SideInfo>,
) -> Result<(Vec<u8>, EncodeQuality), StegoError>

Encode with Ghost mode + shadows and return the encode quality score.