Update what's new for 1.3.0.M2

Author: acogoluegnes

src/docs/asciidoc/new.adoc

@@ -8,7 +8,11 @@
 * Allow passive exchange and queue declaration
 * Emit exception on server-initiated channel closing in publish confirms
 flow
-* Use Java client 5.7.1
+* Add support for handling returned (undeliverable) messages in `Sender`
+* Add hook to configure `Mono<Connection>`
+* Support client-generated consumer tags
+* Cache connections and channels only on success
+* Use Java client 5.7.3
 
 === What's new in Reactor RabbitMQ 1.2