message: fix: make translation module type check correctly
diff: import Translator from './Translator';
  import { TranslatorConfig } from './types';
  -let singleton: Translator;
  +let singleton: Translator | undefined;
  let isConfigured = false;
  function configure(config?: TranslatorConfig) {
  @@ -15,10 +15,11 @@ function configure(config?: TranslatorConfig) {
  function getInstance() {
  if (!isConfigured) {
  - console.warn('You must call configure(...) before calling other methods');
  - if (!singleton) {
  - singleton = new Translator();
  + console.warn('You should call configure(...) before calling other methods');
  }
  +
  + if (typeof singleton === 'undefined') {
  + singleton = new Translator();
  }
  return singleton;
  