Update release notes

Signed-off-by: Idlir Shkurti <[email protected]>

Author: idlir-shkurti-frequenz

RELEASE_NOTES.md

@@ -21,6 +21,7 @@
 ## New Features
 
 - Warning messages are logged when multiple instances of `*Pool`s are created for the same set of batteries, with the same priority values.
+- Add a `ModelManager` class to load, monitor and update machine learning models.
 
 ## Bug Fixes