dev: Update CHANGELOG

Author: happyRip

CHANGELOG.md

@@ -11,6 +11,7 @@ For details about compatibility between different releases, see the **Commitment
 
 ### Added
 
+- `Count` RPC on `EndDeviceRegistry` to efficiently retrieve the number of end devices in an application.
 - Add tracing for LBS LNS and TTIGW protocol handlers.
 - TTGC LBS Root CUPS claiming support.
 - Configurable Identity Server user login session TTL via `is.user-login.session-ttl`: