[FEATURE] Dashboard widget: TYPO3 security advisories

A new widget is added which displays a list of security
advisories from the typo3.org RSS feed.

Resolves: #90512
Releases: master
Change-Id: Ie01eb859c8f434efea7383e43134aafa251fdc10
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/63397


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Kay Strobach <typo3@kay-strobach.de>
Tested-by: Richard Haeser <richard@maxserv.com>
Reviewed-by: Kay Strobach <typo3@kay-strobach.de>
Reviewed-by: Richard Haeser <richard@maxserv.com>