[TASK] RTE: Update some references to core documentation

Update the references to core documentation using cross-linking.

Releases: master, 6.2
Resolves: #62843
Change-Id: Ia31aa8436ac4c897dd4799372048f12c68351bd5
Reviewed-on: http://review.typo3.org/34273
Reviewed-by: Stanislas Rolland <typo3@sjbr.ca>
Tested-by: Stanislas Rolland <typo3@sjbr.ca>