[DOCS] Add note about TSconfig behaviour in EXT:linkvalidator

The EXT:linkvalidator documentation is extended to
include a note about the behaviour and usage of page
TSconfig when recursively checking for broken links.

Resolves: #84887
Releases: master, 10.4, 9.5
Change-Id: I183bc3fdf734db1a871a509fafd6b82d75ea16aa
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/69407
Tested-by: core-ci <typo3@b13.com>
Tested-by: Sybille Peters <sypets@gmx.de>
Tested-by: Richard Haeser <richard@richardhaeser.com>
Reviewed-by: Sybille Peters <sypets@gmx.de>
Reviewed-by: Richard Haeser <richard@richardhaeser.com>

typo3/sysext/linkvalidator/Documentation/Configuration/Index.rst

@@ -18,6 +18,13 @@ You can find the standard configuration in
 This may serve as an example on how to configure the extension for
 your needs.
 
+.. note::
+
+   When checking for broken links in the TYPO3 backend module or the
+   corresponding scheduler task, the page TSconfig of the selected start
+   page is also applied to all subpages - when checking recursive.
+   In case subpages should behave differently and therefore contain a
+   different linkhandler configuration, they must be checked individually.
 
 Minimal Configuration
 ^^^^^^^^^^^^^^^^^^^^^