Support for none

[svgeesus]

We currently don't accept the keyword none, nor do we generate it on serialization.

[svgeesus]

Even when we generate a color with NaN as the hue, we still serialize it as 0: rgba(0 0 0 / 0) converts to Oklch with the coordinates [0, 0, NaN] and we serialize as oklch(0 0 0 / 0)

[svgeesus]

Culprit is in serialize.js

	// Convert NaN to zeros to have a chance at a valid CSS color
	// Also convert -0 to 0
	// This also clones it so we can manipulate it
	coords = coords.map(c => c? c : 0);

[LeaVerou]

So there are two components to this:

• Support parsing none (convert it to NaN)
• Support outputting none

The last bit is tricky: we want serialize() to output none, but display() should not unless the browser actually supports it. So, the only way I see to do this, is to

• add an option to serialize() which converts NaN to 0 (the current default, which should now be the not-default — I think the compat risk here is minimal).

Then, if the color has NaN components,

• display() can check if none is supported, and use the appropriate option.

[LeaVerou]

Done, we can probably close this now.
In the end display() does its own stripping of none so we ended up not needing the option in serialize() so I removed it.

[svgeesus]

@LeaVerou our color parsing tests are still failing because they expect to find NaN in coords but find null instead.

[LeaVerou]

@LeaVerou our color parsing tests are still failing because they expect to find NaN in coords but find null instead.

They're all passing, so closing this again