docs(slideover): update

docs/app/components/content/examples/slideover/SlideoverOpenExample.vue

@@ -0,0 +1,17 @@
+<script setup lang="ts">
+const open = ref(false)
+
+defineShortcuts({
+  o: () => open.value = !open.value
+})
+</script>
+
+<template>
+  <USlideover v-model:open="open">
+    <UButton label="Open" color="gray" variant="subtle" />
+
+    <template #content>
+      <Placeholder class="h-full m-4" />
+    </template>
+  </USlideover>
+</template>