cssValue function
Converts typed style values into CSS strings.
Implementation
String cssValue(Object? value, {bool unitlessNumber = false}) {
if (value == null) return '';
if (value is TokenRef) return value.toCss();
if (value is SizeValue) return value.value;
if (value is Flex) return value.toCss();
if (value is Border) return value.toCss();
if (value is Shadow) return value.toCss();
if (value is num) return unitlessNumber ? value.toString() : '${value}px';
return value.toString();
}