requestLanguages(requestedLangs) {
    super.requestLanguages(requestedLangs).then(
      () => this.translateRoots()
    );
  }
Trigger the language negotation process with an array of language codes.
Returns a promise with the negotiated array of language objects as above.

```javascript
localization.requestLanguages(['de-DE', 'de', 'en-US']);
```

@param   {Array<string>} requestedLangs - array of requested languages
@returns {Promise<Array<string>>}