Update release notes

Author: juan-g-bonilla

docs/source/Support/bskReleaseNotes.rst

@@ -88,7 +88,11 @@ Version |release|
 - Fixed a bug where :ref:`spinningBodyOneDOFStateEffector` and :ref:`spinningBodyNDOFStateEffector`
   both registered their states under the same name, resulting in overwriting and a ``BSK_ERROR``.
 - Added support for :ref:`hingedRigidBodyStateEffector` to be the parent for Dynamic Effectors.
-
+- Added ``SysModelMixin``, a utility class in ``py_sys_model.i`` that can be used for subclasses
+  of ``SysModel`` that have virtual methods to be implemented in Python. The class will automatically
+  add better error logging for all methods implemented in Python and will add a sanity check that the
+  C++ class constructor is called (otherwise, hard-to-parse errors will be raised). Refactored
+  ``pyStatefulSysModel.i`` to use this mixin.
 
 Version 2.8.0 (August 30, 2025)
 -------------------------------