feat: readme toc dropdown scroll to the selected item position

Author: btea

app/components/ReadmeTocDropdown.vue

@@ -139,6 +139,23 @@ function handleKeydown(event: KeyboardEvent) {
       break
   }
 }
+
+const itemScrollIntoView = (index: number) => {
+  const item = props.toc[index]
+  if (!item) return
+  const el = document.getElementById(`${listboxId}-${item.id}`)
+  if (el) {
+    el.scrollIntoView({ block: 'center'})
+  }
+} 
+
+watch(isOpen, (open) => {
+  if (open && highlightedIndex.value >= 0) {
+    itemScrollIntoView(highlightedIndex.value)
+  }
+}, {
+  flush: 'post',
+})
 </script>
 
 <template>