[TASK] Raise TYPO3 version to 8 LTS

[cseifert]

Thanks for that great extension. I tested your extension under 8 LTS and it works as expected.

[dhuf]

@cseifert I would suggest 8.7 instead of only 8.6, if it is working of course

[cseifert]

@dhuf Done. It works with 8.7 as well.

[mkoehler2911]

Thanks for upgrading for Typo3 8!
I'm using Typo3 8.7.7 composer installation. After activating your extension I got this error:

Could you help?
Thanks!