docs: function unit(value, property) {
  	let ignored = ['font-weight', 'opacity', 'content', 'columns', 'column-count'];
  
  	if (ignored.includes(property) || property === false || value === 0 || /\s/.test(value)) {
  		return value.toString();
  	}
  
  	if (! isUnit(value) && isNumber(value)) {
  		if (property === 'line-height') {
  			value += units.lineHeight;
  		} else {
  			value += units.default;
  		}
  	}
  
  	return value;
  }