Prepare changelog for upcoming release

Author: urfeex

ur_simulation_gz/CHANGELOG.rst

@@ -2,6 +2,12 @@
 Changelog for package ur_simulation_gz
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+Forthcoming
+-----------
+* Add support for UR18 (`#118 <https://github.com/UniversalRobots/Universal_Robots_ROS2_GZ_Simulation/issues/118>`_)
+* Add migration notes to package docs (`#117 <https://github.com/UniversalRobots/Universal_Robots_ROS2_GZ_Simulation/issues/117>`_)
+* Contributors: Felix Exner, URJala
+
 2.4.0 (2025-09-18)
 ------------------
 * Add launch support for UR8 Long (`#111 <https://github.com/UniversalRobots/Universal_Robots_ROS2_GZ_Simulation/issues/111>`_)