wip/go-dither 2.4.0 NetBSD

dither is a library for dithering images in Go. It has many dithering algorithms built-in, and allows you to specify your own. Correctness is a top priority, as well as performance. It is designed to work well on its own, but also implements interfaces from the standard library, so that it can be integrated easily in a wide variety of situtations. It supports images that make use of the alpha channel, AKA transparency.