Updated RELEASE_NOTES.

RELEASE_NOTES.md

@@ -6,6 +6,8 @@ Changed defaults: for newly created instances, `disable_inbox_collection` and `d
 
 New admin configuration option: if the `purge_static` value is set to `true` in `server.json`, each user's static directory is explored and those files there that are no longer attached to any post or referenced anywhere are deleted. See `snac(8)` for more information about those cases where you may not want to enable this option.
 
+Allow serving files from subdirectories of the `static/` subdirectory (contributed by la_ninpre).
+
 ## 2.91
 
 Fixed some local posts not being shown if the replied post is deleted.