function applyLanguageSetting(settings, languageCode) {
  var normalizedLanguageCode = normalizeLanguageCode(languageCode);

  if ((0, _dictionariesManager.hasLanguageDictionary)(normalizedLanguageCode)) {
    settings.language = normalizedLanguageCode;
  } else {
    settings.language = _dictionariesManager.DEFAULT_LANGUAGE_CODE;
    warnUserAboutLanguageRegistration(languageCode);
  }
}
Set proper start language code. User may set language code which is not proper.

@param {Object} settings Settings object.
@param {String} languageCode Language code for specific language i.e. 'en-US', 'pt-BR', 'de-DE'.
@returns {String}