Add release notes for 2.1.2

Author: FBumann

CHANGELOG.md

@@ -7,6 +7,16 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [2.1.2] - 2025-06-14
+
+### Fixed
+- Storage losses per hour where not calculated correctly, as mentioned by @brokenwings01. This might have lead to issues with modeling large losses and long timesteps. 
+  - Old implementation:     $c(\text{t}_{i}) \cdot (1-\dot{\text{c}}_\text{rel,loss}(\text{t}_i)) \cdot \Delta \text{t}_{i}$
+  - Correct implementation: $c(\text{t}_{i}) \cdot (1-\dot{\text{c}}_\text{rel,loss}(\text{t}_i)) ^{\Delta \text{t}_{i}}$
+
+### Known issues
+- Just to mention: Plotly >= 6 may raise errors if "nbformat" is not installed. We pinned plotly to <6, but this may be fixed in the future.
+
 ## [2.1.1] - 2025-05-08
 
 ### Fixed