Add MDN link for toggle event

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Author: NullVoxPopuli

ember-primitives/src/components/menu.gts

@@ -154,6 +154,7 @@ const installContent = eModifier<{
 }>((element, _: [], { isOpen, triggerElement }) => {
   // Focus first focusable element when the popover opens.
   // The toggle event fires natively after showPopover() completes.
+  // https://developer.mozilla.org/en-US/docs/Web/API/HTMLElement/toggle_event
   function onToggle(e: ToggleEvent) {
     if (e.newState !== "open") return;