docs: fix vue example

examples/nuxt-example/components/ui/form/FormItem.vue

@@ -0,0 +1,19 @@
+<script lang="ts" setup>
+import { type HTMLAttributes, provide } from 'vue'
+import { useId } from 'radix-vue'
+import { FORM_ITEM_INJECTION_KEY } from './injectionKeys'
+import { cn } from '@/lib/utils'
+
+const props = defineProps<{
+  class?: HTMLAttributes['class']
+}>()
+
+const id = useId()
+provide(FORM_ITEM_INJECTION_KEY, id)
+</script>
+
+<template>
+  <div :class="cn('space-y-2', props.class)">
+    <slot />
+  </div>
+</template>