feat: add useId utility function

src/util.ts

-import { computed, ComputedGetter, ComputedRef } from 'vue'
+import { computed, ComputedGetter, ComputedRef, readonly, ref } from 'vue'
 
 export function computedIter<T>(fn: ComputedGetter<Iterable<T>>): ComputedRef<T[]> {
   return computed(() => Array.from(fn()))
 }
+
+export const useId = (() => {
+  let _id = 0
+  return function useId(prefix = 'component') {
+    return readonly(ref(`${prefix}-${_id++}`))
+  }
+})()