Add support for Float RGB

[quinton-ashley]

In CSS color(srgb ...) and color(display-p3 ...) use the new float (0-1) rgb format.

I think the legacy 8-bit (0-255), integer rgb format should remain the default for the q2d renderer, but for the upcoming webgpu renderer the float rgb format should be the default, since it's also the default color format for all of webgpu's color formats, regardless of color space.

The updated colorMode(mode, colorFormat) function will take two params: a mode ('rgb', 'srgb', or 'oklch') and a colorFormat ('integer' or 'float').

colorMode('rgb', 'float');

The current integer RGBA color classes will be renamed:

ColorRGBA_8
ColorRGBA_P3_8

The float color classes will be named:

ColorRGBA
ColorRGBA_P3