[DOCS] Add 12.4.x directory to changelogs

Resolves: #100741
Releases: main
Change-Id: I0f65275282c85ce005eac85a081da7139606ceda
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/78836


Reviewed-by: Jasmina Ließmann <minapokhalo+typo3@gmail.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: Jasmina Ließmann <minapokhalo+typo3@gmail.com>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Chris Müller <typo3@krue.ml>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>