adding readme

Signed-off-by: Tihomir Surdilovic <tihomir@temporal.io>

Author: tsurdilo

core/src/main/java/io/temporal/samples/packetdelivery/README.md

@@ -0,0 +1,10 @@
+# Async Package Delivery Sample
+
+This sample show how to run multiple "paths" of execution async within single workflow.
+Sample starts deliveries of 5 items in parallel. Each item performs an activity
+and then waits for a confirmation signal, then performs second activity.
+
+Workflow waits until all packets have been delivered. Each packet delivery path can choose to
+also "cancel" delivery of another item. This is done via signal and cancellation of the 
+CancellationScope. 
+