docs(select-menu): update

docs/app/components/content/examples/select-menu/SelectMenuOpenExample.vue

@@ -0,0 +1,13 @@
+<script setup lang="ts">
+const open = ref(false)
+const items = ref(['Backlog', 'Todo', 'In Progress', 'Done'])
+const selected = ref('Backlog')
+
+defineShortcuts({
+  o: () => open.value = !open.value
+})
+</script>
+
+<template>
+  <USelectMenu v-model="selected" v-model:open="open" :items="items" />
+</template>