Update release notes

Signed-off-by: cwasicki <[email protected]>

Author: cwasicki

RELEASE_NOTES.md

@@ -10,7 +10,7 @@
 
 ## New Features
 
-<!-- Here goes the main new features and examples or instructions on how to use them -->
+* Adds a configuration class for microgrids copied from `frequenz-floss/lib-notebooks`.
 
 ## Bug Fixes