docs: Add deprecation notice to readme (#896)

README.md

@@ -1,5 +1,19 @@
 Open edX Data Pipeline
 ======================
+
+# DEPRECATION NOTICE
+
+The Insights product and associated repositories are in the process of being 
+deprecated and removed from service. Details on the deprecation status and
+process can be found in the relevant [Github issue](https://github.com/openedx/public-engineering/issues/221).
+
+This repository may be archived and moved to the openedx-unsupported
+Github organization at any time.
+
+The following sections are for historical purposes only.
+
+---
+
 A data pipeline for analyzing Open edX data. This is a batch analysis engine that is capable of running complex data processing workflows.
 
 The data pipeline takes large amounts of raw data, analyzes it and produces higher value outputs that are used by various downstream tools.