code: function createCssRule(selector, ...rules) {
      let styles = document.getElementById(styleId);
  
      if (!styles) {
          styles = document.createElement('style');
          styles.type = 'text/css';
          styles.id = styleId;
          document.getElementsByTagName('head')[0].appendChild(styles);
      }
  
      const sheet = styles.sheet;
  
      // add each rule via 'insertRule' if that rule doesn't already exist
      // (needed due to storybook / webpack hot reloading)
      for (let i = 0; i < rules.length; i++) {
          const rule = rules[i];
          const cssText = `${selector} { ${rule}; }`;
          let found = false;
  
          for (let j = 0; j < sheet.cssRules.length; j++) {
              const existingRule = sheet.cssRules[j];
              if (cssText === existingRule.cssText) {
                  found = true;
                  break;
              }
          }
  
          if (!found) {
              // insertRule won't allow semicolons
              sheet.insertRule(cssText.replace(';', ''), 0);
          }
      }
  }
docs: Creates a style rule.
  Usage:
  createCssRule(
  '.red-bold',
  'color: #f00; font-weight: bold'
  )
  @param selector
  @param rules