[TASK] Synchronize RST files

* Various .rst file index fixes, NotScanned usually does not make
  sense on Important- and Feature- files.
* Add a missing extension scanner config
* Sync 7* and 8* folders to other core branches

Resolves: #84141
Releases: master, 8.7, 7.6
Change-Id: Ifc19d774d45395cb30bd51f50d9121af409f48bb
Reviewed-on: https://review.typo3.org/56012


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>

typo3/sysext/core/Documentation/Changelog/7.4/Feature-33071-AddTheHttpHeaderContent-LanguageWhenRenderingAPage.rst

@@ -10,10 +10,10 @@ See :issue:`33071`
 Description
 ===========
 
-By default a header "Content-language: XX" is sent where "XX" is the iso code of the sys_language_content if that is
-properly defined by the sys_language record representing the sys_language_uid.
-The "config.disableLanguageHeader" will disable that.
-
+By default a header "Content-language: XX" is sent where "XX" is the iso code of the
+sys_language_content (in the sys_language record, it is represented by the sys_language_isocode field),
+if that is properly defined by the sys_language record representing the sys_language_uid.
+Setting "config.disableLanguageHeader" disables that.
 
 
 Impact