Add sunset notice for ServiceInsight (#1641)

Author: soujay

README.md

@@ -1,5 +1,12 @@
 # ServiceInsight
 
+## 🚨 Sunset Notice
+
+**ServiceInsight has been officially sunsetted.**  
+Its core features have been moved to **ServicePulse**, which is now the recommended tool for monitoring and debugging distributed systems. New development on ServiceInsight has stopped.
+
+## Overview
+
 ServiceInsight provides essential insights for distributed solutions. Verifying that large distributed solutions function correctly is no easy task, especially with many asynchronous and loosely-coupled processes. ServiceInsight gives you visibility across queues, processes, and machines showing messages whose processing has failed (and for what reason) as well as their relation to other messages.
 
 It is part of the [Particular Service Platform](https://particular.net/service-platform), which includes [NServiceBus](https://particular.net/nservicebus) and tools to build, monitor, and debug distributed systems.