Update 0.5 release notes

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

@@ -60,6 +60,7 @@ Please refer to [Pre-fetching relations](../../models-and-databases/queries.md#p
 * Support for the `nil`, `true`, and `false` literals was added to the Marten templating language. Please refer to [Literal values](../../templates/introduction.md#literal-values) for more details on supported literals.
 * The [`assign`](../../templates/reference/tags.md#assign) template tag now supports an `unless assigned` suffix which allows to specify that the assignment must happen only if no variable with the same name is already present in the template context.
 * The [`include`](../../templates/reference/tags.md#include) template tag now supports `isolated` and `contextual` suffixes that allow specifying whether the included templates should have access to the outer context variables. Unless specified, the default behavior is controlled by the new [`templates.isolated_inclusions`](../../development/reference/settings.md#isolated_inclusions) setting.
+* A new [`capture`](../../templates/reference/tags.md#capture) template tag was introduced to make it possible to easily assign the output of a block of code to a new variable.
 
 #### Development