[TASK] Improve overall readability of sys ext README files

Releases: main
Resolves: #96228
Change-Id: I680bf20c1a3dc63003cf1638ec680ca6ab07447f
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/72492


Tested-by: core-ci <typo3@b13.com>
Tested-by: Susanne Moog <look@susi.dev>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Susanne Moog <look@susi.dev>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>