Intent to prototype and ship: display-p3-linear color space for CSS colors

[Emilio Cobos Álvarez]

Hi,

In bug 1996318 I'm adding the display-p3-linear color space to CSS
colors. This is a relatively minor addition that other browsers support
or are implementing.

Spec: https://drafts.csswg.org/css-color/#predefined-display-p3-linear
Platform coverage: All
Pref: None
DevTools bug: N/A
Standards position:
https://github.com/mozilla/standards-positions/issues/1311
Other browsers:
* Blink: In the process of shipping
* WebKit: Shipping
WPT: https://wpt.fyi/results/css/css-color?q=display-p3-linear

Thanks,

-- Emilio