function getGroups(groupsConfig, twConfig = null) {
  const groups = [];
  groupsConfig.forEach((group) => {
    // e.g. SIZING or SPACING
    group.members.forEach((prop) => {
      // e.g. Width or Padding
      if (typeof prop.members === 'string') {
        // Unique property, like `width` limited to one value
        groups.push(prop.members);
      } else {
        // Multiple properties, like `padding`, `padding-top`...
        prop.members.forEach((subprop) => {
          groups.push(subprop.members);
        });
      }
    });
  });
  if (twConfig === null) {
    return groups;
  }
  return groups.map((re) => patchRegex(re, twConfig));
}
Generates a flatten array from the groups config

@param {Array} groupsConfig The array of objects containing the regex
@param {Object} twConfig The merged config of Tailwind CSS
@returns {Array} Flatten array