chore: updated UPGRADE.md

UPGRADE.md

@@ -2,6 +2,16 @@
 
 _All `MAJOR` version bumps will have upgrade notes posted here._
 
+## [2023-10-17] 4.x.x to 5.x.x-rc.x
+
+---
+### Overview
+
+#### Twilio Node Helper Library’s major version 5.0.0-rc.x is now available. We ensured that you can upgrade to Node helper Library 5.0.0-rc.x version without any breaking changes
+
+Support for JSON payloads has been added in the request body
+
+
 ## [2023-01-25] 3.x.x to 4.x.x
 
 ---