[BUGFIX] Wait with replacing CKEditor until DOM is ready

Resolves: #81243
Releases: master, 8.7
Change-Id: I31ce2b3b97b47c557b93341b17839174e5097e38
Reviewed-on: https://review.typo3.org/53453


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>