[TASK] Disallow access to documentation folders

Update the default .htaccess file. The users must update their
actual configuration (.htaccess or server config) manually.

Resolves: #75934
Releases: master, 7.6, 6.2
Change-Id: I8e40263c72f68c44cb8fd8c1944a44e4d38d9daa
Reviewed-on: https://review.typo3.org/47930


Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Daniel Goerz <ervaude@gmail.com>
Tested-by: Daniel Goerz <ervaude@gmail.com>
Reviewed-by: Nicole Cordes <typo3@cordes.co>
Reviewed-by: Frank Naegler <frank.naegler@typo3.org>
Tested-by: Frank Naegler <frank.naegler@typo3.org>