update release notes

Author: FabianHofmann

doc/release_notes.rst

@@ -2,15 +2,35 @@ Release Notes
 =============
 
 .. Upcoming Version
-* Add ``mock_solve`` option to model.solve for quick testing without actual solving
-* Bugfix for missing dependency for jupyter notebook example in documentation
+
+Version 0.6.0
+--------------
+
+**Features**
+
+* Add ``mock_solve`` option to ``Model.solve()`` for quick testing without actual solving
 * Add support for SOS1 and SOS2 (Special Ordered Sets) constraints via ``Model.add_sos_constraints()`` and ``Model.remove_sos_constraints()``
-* Add simplify method to LinearExpression to combine duplicate terms
-* Add convenience function to create LinearExpression from constant
-* Fix compatibility for xpress versions below 9.6 (regression)
-* Performance: Up to 50x faster ``repr()`` for variables/constraints via O(log n) label lookup and direct numpy indexing
-* Performance: Up to 46x faster ``ncons`` property by replacing ``.flat.labels.unique()`` with direct counting
-* Add support for GPU-accelerated solver [cuPDLPx](https://github.com/MIT-Lu-Lab/cuPDLPx)
+* Add ``simplify`` method to ``LinearExpression`` to combine duplicate terms
+* Add convenience function to create ``LinearExpression`` from constant
+* Add support for GPU-accelerated solver `cuPDLPx <https://github.com/MIT-Lu-Lab/cuPDLPx>`_
+* Add solver features registry for introspection of solver capabilities
+
+**Performance**
+
+* Up to 50x faster ``repr()`` for variables/constraints via O(log n) label lookup and direct numpy indexing
+* Up to 46x faster ``ncons`` property by replacing ``.flat.labels.unique()`` with direct counting
+
+**Bug Fixes**
+
+* Fix HiGHS solver to properly stop on Ctrl-C keyboard interrupt
+* Fix CBC solver to correctly parse negative objective values
+* Fix Xpress compatibility for versions below 9.6 (regression from namespace change)
+* Fix Xpress ``getDual()`` fallback for older versions
+* Fix missing dependency for jupyter notebook example in documentation
+
+**Solver Updates**
+
+* Add Xpress 9.8+ API support with full backward compatibility to 9.6+
 
 Version 0.5.8
 --------------