HierarchyQueryExt release notes (#1757)

Co-authored-by: Viktor Gustavsson <[email protected]>

Author: alice-i-cecile

release-content/0.15/release-notes/15627_Add_more_tools_for_traversing_hierarchies.md

@@ -1,4 +1,23 @@
 <!-- Add more tools for traversing hierarchies -->
 <!-- https://github.com/bevyengine/bevy/pull/15627 -->
 
-<!-- TODO -->
+We've spruced up the [`HierarchyQueryExt`] [extension trait],
+making it easier to traverse entity hierarchies defined by the [`Parent`] and [`Children`] components.
+
+The full set of methods is now:
+
+- `parent` (new)
+- `children` (new)
+- `root_ancestor` (new)
+- `iter_leaves` (new)
+- `iter_siblings` (new)
+- `iter_descendants`
+- `iter_descendants_depth_first` (new)
+- `iter_ancestors`
+
+All of these operations were previously possible, but we hope that this API makes working with hierarchies more pleasant, especially for UI and animation.
+
+[`HierarchyQueryExt`]: https://docs.rs/bevy/0.15/bevy/hierarchy/trait.HierarchyQueryExt.html
+[`Parent`]: https://docs.rs/bevy/0.15/bevy/hierarchy/struct.Parent.html
+[`Children`]: https://docs.rs/bevy/0.15/bevy/hierarchy/struct.Children.html
+[extension trait]: https://rust-lang.github.io/rfcs/0445-extension-trait-conventions.html

release-content/0.15/release-notes/_release-notes.toml

@@ -410,7 +410,7 @@ prs = [15614]
 file_name = "15614_Allow_Worldentity_family_of_functions_to_take_multiple_ent.md"
 
 [[release_notes]]
-title = "Add more tools for traversing hierarchies"
+title = "More tools for traversing hierarchies"
 authors = ["@alice-i-cecile"]
 contributors = ["@atornity", "@ItsDoot", "@villor"]
 prs = [15627]