docs(input): add examples

docs/app/components/content/examples/input/InputFormFieldExample.vue

@@ -0,0 +1,9 @@
+<script setup lang="ts">
+const email = ref('')
+</script>
+
+<template>
+  <UFormField label="Email" help="We won't share your email." required>
+    <UInput v-model="email" placeholder="Enter your email" icon="i-heroicons-at-symbol" />
+  </UFormField>
+</template>