[Request] Add specialK info to readme

[EtherealIntellect]

Hey there, not sure where to mention this best, but https://www.pcgamingwiki.com/wiki/Special_K can be used to lower latency of the copied shaderglass window, down to +1 frame in windowed mode. Since desktop compositing on windows can already be kind of slow depending on the setup, specialK seems to be the most powerful project at fixing the most common issues that cause window manager latency