Inconsistent emoji colors across platforms

[niminypiminy]

A configuration option to control emoji color rendering would be helpful. On Windows, the backend automatically enables color glyphs, so emojis are always colored and will not respect monochrome unless explicitly disabled. even using FE0E often has no effect.

[nicoburns]

We should support the font-variant-emoji CSS property. I believe this will also require support in Parley/Fontique. I've opened an issue there linebender/parley#492

[niminypiminy]

thank you.