getBrowserLang() not working on IE11

[rbirkgit]

Current behavior

On IE11 getBrowserLang() always returns 'en' for us even though the language settings are set to German (or other languages).

Expected behavior

Return the correct language

How do you think that we should fix this?

Return the correct language

Minimal reproduction of the problem with instructions

Set the language on IE11 to German

Environment

ngx-translate version: 10.0.2
Angular version: 6.1.9


Browser:
- [ ] Chrome (desktop) version XX
- [ ] Chrome (Android) version XX
- [ ] Chrome (iOS) version XX
- [ ] Firefox version XX
- [ ] Safari (desktop) version XX
- [ ] Safari (iOS) version XX
- [x] IE version 11
- [ ] Edge version XX
 
For Tooling issues:
- Node version: XX  
- Platform:  

Others: