docs(collapsible): update

docs/app/components/content/examples/collapsible/CollapsibleIconExample.vue

@@ -0,0 +1,17 @@
+<template>
+  <UCollapsible class="w-48 mx-auto">
+    <UButton
+      class="group"
+      label="Open"
+      color="gray"
+      variant="subtle"
+      trailing-icon="i-heroicons-chevron-down-20-solid"
+      :ui="{ trailingIcon: 'group-data-[state=open]:rotate-180 transition-transform duration-200' }"
+      block
+    />
+
+    <template #content>
+      <Placeholder class="h-48" />
+    </template>
+  </UCollapsible>
+</template>