Implementing grayscale support for B&W displays

[ZtereoHYPE]

Hello, I am using this crate with an e-paper 2.9" v2 screen, but noticed the lack of grayscale support. Since I will have to implement it to finish my project, it would be nice to be able to PR the grayscale support after I'm done such that other people can benefit from it. I write here to ask how this code should be structured in order to potentially be incorporated into the crate.

The author of #129 briefly discussed this, and the reached consensus was that if there are no additional latency or refresh rate concerns, then the panels should always be initialised with the grayscale LUTs / mode enabled. However, I do not possess any equipment (or experience, really) to be able to test that. Should I still proceed on that path?