add swap method and update comments

crates/bevy_transform/src/components/children.rs

@@ -23,6 +23,11 @@ impl Children {
     pub fn with(entity: &[Entity]) -> Self {
         Self(SmallVec::from_slice(entity))
     }
+
+    /// Swaps the child at `a_index` with the child at `b_index`
+    pub fn swap(&mut self, a_index: usize, b_index: usize) {
+        self.0.swap(a_index, b_index);
+    }
 }
 
 impl Deref for Children {

examples/ecs/hierarchy.rs

@@ -110,9 +110,6 @@ fn rotate(
 
         // To demonstrate removing children, we'll start to remove the children after a couple of seconds
         if time.seconds_since_startup >= 2.0 && children.len() == 3 {
-            // Using .despawn() on an entity does not remove it from its parent's list of children!
-            // It must be done manually if using .despawn()
-            // NOTE: This is a bug. Eventually Bevy will update the children list automatically
             let child = children.last().copied().unwrap();
             commands.despawn(child);
         }