languagesByGroup = (languages, groupIdentifier) => {
  const groupName = groupIdentifier.replace(":", "");
  return languages.filter((el) => el.categories.includes(groupName));
}
Filters languages by group (common, etc)

Groups are currently defined inside each language file with `Category`

@param {array<Language>} languages full list of languages
@returns {array<Language>} filtered list