add readme

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

Author: tsurdilo

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

@@ -0,0 +1,15 @@
+# Auto-heartbeating sample for activities that define HeartbeatTimeout
+
+This sample shows an implementation of an "auto-heartbeating" utility that can be applied via interceptor
+to all activities where you define HeartbeatTimeout. Use case where this can be helpful include
+situations where you have long-running activities where you want to heartbeat but its difficult 
+to explicitly call heartbeat api in activity code directly. 
+
+1. Start the Sample:
+```bash
+./gradlew -q execute -PmainClass=io.temporal.samples.autoheartbeat.Starter
+```
+
+The sample workflow starts three activities async, two of which define heartbeat timeout. 
+Activity interceptor in this sample applies the auto-heartbeating util to the two that define heartbeat timeout
+and auto-heartbeats at its HeartbeatTimeout - 1s intervals.