The document references files that do not exist anymore, also CONTRIBUTING.md
is missing.

* ChangeLog => gone
* GPL.txt => LICENSE.txt
* NEWS.txt => gone

Resolves: #82698
Releases: master, 8.7
Change-Id: Idb5890f789632a342d1d640febd4ac1b9fa7497b
Reviewed-on: https://review.typo3.org/54320


Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>