function getGroupConfigKeys(groupsConfig) {
  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.configKey ? prop.configKey : null);
      } else {
        // Multiple properties, like `padding`, `padding-top`...
        prop.members.forEach((subprop) => {
          groups.push(subprop.configKey ? subprop.configKey : null);
        });
      }
    });
  });
  return groups;
}
Generates a flatten array from the groups configKeys

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