docs(input): add examples

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

@@ -0,0 +1,26 @@
+<script setup lang="ts">
+const value = ref('')
+const domains = ['.com', '.dev', '.org']
+const domain = ref(domains[0])
+</script>
+
+<template>
+  <UButtonGroup>
+    <UInput
+      v-model="value"
+      placeholder="nuxt"
+      :ui="{
+        base: 'pl-[57px]',
+        leading: 'pointer-events-none'
+      }"
+    >
+      <template #leading>
+        <p class="text-sm text-[var(--ui-text-muted)]">
+          https://
+        </p>
+      </template>
+    </UInput>
+
+    <USelectMenu v-model="domain" :items="domains" />
+  </UButtonGroup>
+</template>