added example to readme

README.md

@@ -3,4 +3,12 @@ Does quantization in pure rust on Rgba image, using https://crates.io/crates/ima
 algorithm:
 https://observablehq.com/@tmcw/octree-color-quantization
 
-inspired by to https://github.com/objectProfessionals/movieMaps
+inspired by to https://github.com/objectProfessionals/movieMaps
+
+fn test_big_image() -> Result<(), ImageError> {
+    let src: RgbaImage = image::open("some_image.jpg").unwrap().into_rgba8();
+
+    let out = quantize(&src, 256);
+    out.save_with_format("output.jpg", image::ImageFormat::Jpeg)?;
+    Ok(())
+}