Updated RELEASE_NOTES.

RELEASE_NOTES.md

@@ -2,6 +2,8 @@
 
 ## UNRELEASED
 
+Purged local posts now generate a `Delete` activity that is sent everywhere, instead of only deleted from the filesystem.
+
 Included a small tweak to avoid being confused by implementations that return valid webfinger queries for non-account URLs (like i.e. the Wordpress ActivityPub plugin in some configurations).
 
 Added Ukrainian translation (contributed by wincentbalin).