add section about notifying implementors

RELEASING_RAILS.rdoc

@@ -14,6 +14,20 @@ Today is mostly coordination tasks.  Here are the things you must do today:
 Let them know of your plans to release.  There may be security issues to be
 addressed, and that can impact your release date.
 
+=== Notify implementors.
+
+Ruby implementors have high stakes in making sure Rails works.  Be kind and
+give them a heads up that Rails will be released soonish.
+
+Send an email just giving a heads up about the upcoming release to these
+lists:
+
+* team@jruby.org
+* community@rubini.us
+* rubyonrails-core@googlegroups.com
+
+Implementors will love you and help you.
+
 === Is the CI green?  If not, make it green. (See "Fixing the CI")
 
 Do not release with a Red CI.  You can find the CI status here: