chore(playground): improve design

playground/app.vue

@@ -1,7 +1,23 @@
 <template>
   <UContainer class="min-h-screen flex items-center">
-    <UCard class="flex-1 text-center">
+    <UCard class="flex-1" :ui="{ background: 'bg-gray-50 dark:bg-gray-800/50', ring: 'ring-1 ring-gray-300 dark:ring-gray-700', divide: 'divide-y divide-gray-300 dark:divide-gray-700', header: { base: 'font-bold' } }">
+      <template #header>
         Welcome to the playground!
+      </template>
+
+      <p class="text-gray-500 dark:text-gray-400">
+        Try your components here!
+      </p>
     </UCard>
   </UContainer>
 </template>
+
+<script setup>
+
+</script>
+
+<style>
+body {
+  @apply antialiased font-sans text-gray-700 dark:text-gray-200 bg-white dark:bg-gray-900;
+}
+</style>