[TASK] Allow access to visible content within /.well-known/ directory

Allow access to the visible content from within the `/.well-known/`
hidden directory. The access to all other hidden files and directories
(starting with a dot) is still blocked.

The /.well-known/ directory represents the standard (RFC 5785) path
prefix for "well-known locations", and therefore, access to its visible
content should not be blocked.

Change-Id: I533d38a12da5cae59abed4fc00d597814d28fa04
Resolves: #72712
Releases: master,7.6,6.2
Reviewed-on: https://review.typo3.org/45901


Reviewed-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Tested-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>