[TASK] Add SECURITY.md

Resolves: #92037
Releases: master, 10.4, 9.5
Change-Id: I1278496485ead10a46f82c1d681db1e48a0aac1d
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/65304


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Oliver Hader <oliver.hader@typo3.org>
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>