feat(SelectMenu): handle async search (#426)

Co-authored-by: Benjamin Canac <canacb1@gmail.com>

docs/content/3.forms/4.select-menu.md

@@ -149,6 +149,40 @@ props:
 ---
 ::
 
+### Async search
+
+Pass a function to the `searchable` prop to customize the search behavior and filter options according to your needs. The function will receive the query as its first argument and should return an array.
+
+Use the `debounce` prop to adjust the delay of the function.
+
+::component-example
+#default
+:select-menu-example-async-search{class="max-w-[12rem] w-full"}
+
+#code
+```vue
+<script setup>
+const search = async (q) => {
+  const users = await $fetch('https://jsonplaceholder.typicode.com/users', { params: { q } })
+
+  return users.map(user => ({ id: user.id, label: user.name, suffix: user.email })).filter(Boolean)
+}
+
+const selected = ref([])
+</script>
+
+<template>
+  <USelectMenu
+    v-model="selected"
+    :searchable="search"
+    placeholder="Search for a user..."
+    multiple
+    by="id"
+  />
+</template>
+```
+::
+
 ## Slots
 
 ### `label`