[DOCS] Add RTE preset override for flexform field

Add the specific way to override a RTE configuration preset for a
flexform field

Resolves: #92102
Releases: master, 10.4, 9.5
Change-Id: I88a621aff48c43833cf5ee9a8e97403322a33a05
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/65460
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Jörg Bösche <typo3@joergboesche.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Jörg Bösche <typo3@joergboesche.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>

typo3/sysext/rte_ckeditor/Documentation/Configuration/ConfigureTypo3.rst

@@ -34,6 +34,10 @@ Page TSconfig can be used to change:
       RTE.config.tt_content.bodytext.preset = myCustomPreset
       RTE.config.tx_news_domain_model_news.bodytext.preset = minimal
 
+#. Override for one field defined in flexform (:ts:`RTE.config.[tableName].[flexForm\.field\.name].preset`)::
+
+      RTE.config.tt_content.settings\.notifications\.emailText.preset = myCustomPreset
+
 #. Override for one field, if type matches (:ts:`RTE.config.[tableName].[fieldName].types.[type].preset`)::
 
       RTE.config.tt_content.bodytext.types.textmedia.preset = minimal