Add deprecation notice

Author: ricellis

CHANGES.md

@@ -1,3 +1,6 @@
+# UNRELEASED
+- [DEPRECATED] This library is now deprecated and will be EOL on Dec 31 2021.
+
 # 4.4.0 (2021-06-18)
 - [FIXED] Parsing of max-age from Set-Cookie headers.
 - [FIXED] Double callback if plugin errors when updating state.

README.md

@@ -1,3 +1,17 @@
+# DEPRECATED
+
+**This library is now deprecated and will be end-of-life on Dec 31 2021.**
+
+The library remains supported until the end-of-life date,
+but will receive only _critical_ maintenance updates.
+
+Please see the [Migration Guide](./MIGRATION.md) for advice
+about migrating to our replacement library
+[cloudant-node-sdk](https://github.com/IBM/cloudant-node-sdk).
+
+For FAQs and additional information please refer to the
+[Cloudant blog](https://blog.cloudant.com/2021/06/30/Cloudant-SDK-Transition.html).
+
 # Cloudant Node.js Client
 
 This is the official Cloudant library for Node.js.