Update NEWS.md

Author: amartinhuertas

NEWS.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.6.9] - 2025.03.15
+
+### Added
+
+- Added `copy` method to `SymSparseMatrixCSR`.
+
 ## [0.6.8] - 2024.08.29
 
 ### Added