Experimental feature: Black crush mitigation

[utopiafallen]

Experimental feature: Black crush mitigation

The OLED display on my Lenovo Chomebook Duet 5 suffers from black crush so this experimental feature adds a custom gamma curve to boost dark values and alleviate the worst of the black crush.

Since this is forked from my master branch, there's a bunch of identical changes as my other pull request. I'm not even sure this "feature" is desirable so I'm leaving the PR in draft mode.

@moonlight-stream