Update 0.5 release notes

docs/docs/the-marten-project/release-notes/0.5.md

@@ -27,6 +27,7 @@ _Under development._
 * A new [`#average`](../../models-and-databases/reference/query-set.md#average) method was introduced to allow computing the average values of a specific model field at the database level for the records targeted by a specific query set.
 * A new [`#sum`](../../models-and-databases/reference/query-set.md#sum) method was introduced to allow computing the sum of the values of a specific model field at the database level for the records targeted by a specific query set.
 * It is now possible to compute the minimum and maximum values of a specific field at the database level for the records targeted by a query set through the use of the [`#minimum`](../../models-and-databases/reference/query-set.md#minimum) and [`#maximum`](../../models-and-databases/reference/query-set.md#maximum) methods.
+* The [`in`](../../models-and-databases/reference/query-set.md#in) query set predicate now supports filtering on arrays of model records directly.
 
 #### Handlers and HTTP