Add release note.

Author: ScoutHarris

RELEASE-NOTES.txt

@@ -6,7 +6,8 @@
 * [**] 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]
 * [*] Stats: fix navigation between Stats tab. [#17856]
-* [*] Quick Start: Fixed a bug where a user logging in via a self-hosted site not connected to Jetpack would see Quick Start when selecting "No thanks" on the Quick Start prompt. [#17855] 
+* [*] Quick Start: Fixed a bug where a user logging in via a self-hosted site not connected to Jetpack would see Quick Start when selecting "No thanks" on the Quick Start prompt. [#17855]
+* [**] Threaded comments: comments can now be moderated via a drop-down menu on each comment. [#17888]
 
 19.1
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