solver: expose omega attribute

usadelndsoc/solver.py

@@ -96,6 +96,7 @@ class Solver:
     y = _core_property("y")
     mask = _core_property("mask")
     Omega = _core_property("Omega")
+    omega = _core_property("omega")
     alpha = _core_property("alpha")
     D = _core_property("D")
     Delta = _core_property("Delta")