function generateOptionalOpacitySuffix(config) {
  const opacityKeys = !config.theme['opacity'] ? [] : Object.keys(config.theme['opacity']);
  opacityKeys.push('\\[(\\d*\\.?\\d*)%?\\]');
  return `(\\/(${opacityKeys.join('|')}))?`;
}
Generates the opacity suffix based on config

@param {Object} config Tailwind CSS Config
@returns {String} The suffix or an empty string