Update release notes

Signed-off-by: Sahas Subramanian <sahas.subramanian@proton.me>

Author: shsms

RELEASE_NOTES.md

@@ -1,17 +1,9 @@
 # Frequenz Microgrid Component Graph Library Release Notes
 
-## Summary
-
-<!-- Here goes a general summary of what this release is about -->
-
 ## Upgrading
 
-<!-- Here goes notes on how to upgrade from previous versions, including deprecations and what they should be replaced with -->
+- The `microgrid` extra now requires `frequenz-client-microgrid >= 0.18.3` (was `>= 0.18.0`) so that the `SteamBoiler` component class is available.
 
 ## New Features
 
-<!-- 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 -->
+- `ComponentGraph` now accepts every component class shipped by `frequenz.client.microgrid.component`.  Battery and EV-charger subtypes (`LiIonBattery`, `NaIonBattery`, `AcEvCharger`, `DcEvCharger`, `HybridEvCharger`) are mapped to their cg-side subtype variant instead of collapsing to `Unspecified`.  Pass-through categories (`Converter`, `CryptoMiner`, `Electrolyzer`, `Hvac`, `Precharger`, `Relay`, `VoltageTransformer`), plus `SteamBoiler` and `UnrecognizedComponent`, are now mapped where they previously raised `ValueError("Unsupported component category: …")`.