print special message for roblox xml

src/main.rs

@@ -344,6 +344,7 @@ fn load_image<R:Read+Seek+std::io::BufRead>(input:&mut R)->AResult<image::Dynami
     match &fourcc{
         b"\x89PNG"=>Ok(image::load(input,image::ImageFormat::Png)?),
         b"\xFF\xD8\xFF\xE0"=>Ok(image::load(input,image::ImageFormat::Jpeg)?),//JFIF
+        b"<rob"=>Err(anyhow::Error::msg("Roblox xml garbage is not supported yet")),
         other=>Err(anyhow::Error::msg(format!("Unknown texture format {:?}",other))),
     }
 }