Update 0.5 release notes

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

@@ -93,6 +93,7 @@ article.category # => Category::BLOG
 
 * The [`collectassets`](../../development/reference/management-commands.md#collectassets) management command now provides the ability to fingerprint collected assets and generate a corresponding JSON manifest. Please refer to [Asset manifests and fingerprinting](../../assets/introduction.md#asset-manifests-and-fingerprinting) to learn more about this capability.
 * The built-in [authentication application](../../authentication/introduction.md) (which can be generated either through the use of the [`new`](../../development/reference/management-commands.md#new) management command or the [`auth`](../../development/reference/generators.md#auth) generator) now uses POST requests when signing out users.
+* A [`play`](../../development/reference/management-commands.md#play) management command was introduced to make it easy to start a Crystal playground server initialized for the current project and open it in the default browser.
 
 #### Security