Clear release notes (#101)

Author: llucax

RELEASE_NOTES.md

@@ -1,9 +1,17 @@
 # Frequenz Core Library Release Notes
 
+## Summary
+
+<!-- Here goes a general summary of what this release is about -->
+
 ## Upgrading
 
-- If you used `enum.DeprecatedMember` directly anywhere, you should probably switch to using `enum.deprecated_member` instead, which will tag the member value with the appropriate type.
+<!-- Here goes notes on how to upgrade from previous versions, including deprecations and what they should be replaced with -->
 
 ## New Features
 
-- A new `enum.deprecated_member` function has been added to create deprecated enum members with proper typing.
+<!-- Here goes the main new features and examples or instructions on how to use them -->
+
+## Bug Fixes
+
+<!-- Here goes notable bug fixes that are worth a special mention or explanation -->