Implement display wakeup on Linux

[thirtythreeforty]

Fixes #27. Based solely on testing on my Ryzen integrated graphics and Dell monitor. All DDC commands sent over DisplayPort. (Ideally none of these details would make a difference, but you never know.)

I attempted to wiggle the mouse, but that worked very inconsistently, while pressing a key works basically every time. I wish there were a truly no-op key to press, but I don't know of one.

[haimgel]

@thirtythreeforty, thanks for the PR, glad you took a look at it. There's a small issue with building on non-Linux machines, though.

[micwoj92]

This branch has conflicts that must be resolved

[haimgel]

Closing in favor of #126