Update RELEASE-NOTES

Author: SiobhyB

RELEASE-NOTES.txt

@@ -2,6 +2,7 @@
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 * [*] Site creation: Fixed bug where sites created within the app were not given the correct time zone, leading to post scheduling issues. [#17821]
 * [*] Block editor: Replacing the media for an image set as featured prompts to update the featured image [https://github.com/wordpress-mobile/gutenberg-mobile/pull/3930]
+* [***] Block editor: Font size and line-height support for text-based blocks used in block-based themes [https://github.com/wordpress-mobile/gutenberg-mobile/pull/4519]
 * [**] Some of the screens of the app has a new, fresh and more modern visual, including the initial one: My Site. [#17812]
 * [**] Notifications: added a button to mark all notifications in the selected filter as read. [#17840]
 * [**] People: you can now manage Email Followers on the People section! [#17854]