docs: fix vue example

examples/nuxt-example/components/ui/dropdown-menu/DropdownMenuGroup.vue

@@ -0,0 +1,11 @@
+<script setup lang="ts">
+import { DropdownMenuGroup, type DropdownMenuGroupProps } from 'radix-vue'
+
+const props = defineProps<DropdownMenuGroupProps>()
+</script>
+
+<template>
+  <DropdownMenuGroup v-bind="props">
+    <slot />
+  </DropdownMenuGroup>
+</template>