onHsv method
Creates chalk with background color defined from HSV (Hue, Saturation and Value) color space parameters. https://en.wikipedia.org/wiki/HSL_and_HSV
Implementation
Chalk onHsv(num hue, num saturation, num value) {
var rgb = ColorUtils.hsv2rgb(hue, saturation, value);
return makeRGBChalk(rgb[0], rgb[1], rgb[2], bg: true);
}