src/language-css/parser-postcss.js/parseValue
function parseValue(value, options) {
  const valueParser = require("postcss-values-parser");

  let result = null;

  try {
    result = valueParser(value, { loose: true }).parse();
  } catch (e) {
    return {
      type: "value-unknown",
      value,
    };
  }

  result.text = value;

  const parsedResult = parseNestedValue(result, options);

  return addTypePrefix(parsedResult, "value-", /^selector-/);
}