message: Add TextEncoder polyfill for test run
diff: import * as languageHandler from "../src/languageHandler";
  +import { TextEncoder, TextDecoder } from 'util';
  languageHandler.setLanguage('en');
  languageHandler.setMissingEntryGenerator(key => key.split("|", 2)[1]);
  require('jest-fetch-mock').enableMocks();
  +
  +// polyfilling TextEncoder as it is not available on JSDOM
  +// view https://github.com/facebook/jest/issues/9983
  +global.TextEncoder = TextEncoder;
  +global.TextDecoder = TextDecoder;
  