code: function printUserUnused() {
    if (!argv.unused) {
      return;
    }
  
    const userUnconfigured = _.difference(rules.stylelintNoDeprecated, rules.userRulesNames);
    let heading;
  
    if (!userUnconfigured.length) {
      heading = chalk.green('All rules are up-to-date!');
      printColumns(heading);
  
      return;
    }
  
    const rulesToPrint = _.map(userUnconfigured, rule => {
      return {
        rule,
        url: chalk.cyan(`https://stylelint.io/user-guide/rules/${rule}/`)
      };
    });
  
    heading = chalk.blue.underline('UNUSED: Available rules that are not configured:');
  
    printColumns(heading, rulesToPrint);
  }
docs: Print available stylelint rules that the user hasn't configured yet