Update CHANGELOG.md

Author: Arto Kinnunen

CHANGELOG.md

@@ -21,6 +21,7 @@ Mesh stack ready for Wi-SUN FAN and PHY certification tests.
 * Improved Wi-SUN asynchronous messaging statistics. Time spent in different states and neighbor management changes.
 * Created API to get the Wi-SUN Neighbor table with basic information from the neighbor.
 * Added support for set MAC and MPX Data Request priority.
+* Implemented Last Gasp support for Wi-SUN devices using Expedite Forward Traffic class packets.
 
 ### Changes
 * Added throttling of number of simultaneous EAPOL authentications based on Border Router TX queue size