Add CHANGELOG entry for .stp file extension support

Co-authored-by: gonzalocasas <[email protected]>

Author: Copilot

CHANGELOG.md

@@ -9,6 +9,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+* Added support for `.stp` file extension in addition to `.step` for `RhinoBrep.from_step()` and `RhinoBrep.to_step()` methods.
+
 ### Changed
 
 * Updated minimum library version to `2.14.1` in Rhino8 GH components.