Update release notes

Signed-off-by: Matthias Wende <[email protected]>

Author: matthias-wende-frequenz

RELEASE_NOTES.md

@@ -10,7 +10,7 @@
 
 ## New Features
 
-<!-- Here goes the main new features and examples or instructions on how to use them -->
+- Add a energy message for electricity trading markets
 
 ## Bug Fixes