Add sqlalchemy.orm.query_expression definition (#100)

Author: isra17

sqlalchemy-stubs/orm/__init__.pyi

@@ -51,6 +51,8 @@ def dynamic_loader(argument, **kw): ...
 column_property = ColumnProperty
 composite = CompositeProperty
 
+def query_expression() -> ColumnProperty: ...
+
 def backref(name, **kwargs): ...
 def deferred(*columns, **kw): ...