Support new color functions

[blfpd]

Grass can build Bulma 1.0.2 but not 1.0.3 because of they use color.channel() function, and the $space argument of color.adjust() and color.scale().

See the SASS documentation on breaking changes

Being fully complient may be hairy, but as a first step we could alias:

@use "sass:color";
$color: #c71585;

color.channel($color, "red", rgb);
/* to: */
color.red($color);

color.channel($color, "green", rgb);
/* to: */
color.green($color);

color.channel($color, "blue", rgb);
/* to: */
color.blue($color);

As for color.adjust(…, $space) maybe assume rgb for now, with a warning?