docs(readme): mention "a dither".

README.md

@@ -14,8 +14,9 @@ It implements its own simple [file format](format.md) and converts between this
 It can also convert normal PNG to normal 32-bit PNG with only high color color values.
 (This simulates a roundtrip through HiColor without creating a temporary file.)
 To reduce the quantization error (the difference between the original and the high-color pixel),
-HiColor uses the [Bayer ordered dithering](https://bisqwit.iki.fi/story/howto/dither/jy/#StandardOrderedDitheringAlgorithm) algorithm, which historical software and hardware used for dithering in high color modes.
-Dithering can be disabled with a command line flag.
+HiColor can use either the [Bayer ordered dithering](https://bisqwit.iki.fi/story/howto/dither/jy/#StandardOrderedDitheringAlgorithm) algorithm or [“a dither”](https://pippin.gimp.org/a_dither/).
+The Bayer algorithm was what historical software and hardware used for dithering in high color mode.
+Dithering can be selected or disabled with command-line flags.
 HiColor files have either the extension `.hic` or `.hi5` for 15-bit and `.hi6` for 16-bit respectively.
 
 Quantized images compress better when their originals, so HiColor may serve as a less-lossy alternative to the 256-color [pngquant](https://pngquant.org/).