fix: add missing import

src/runtime/plugin.client.ts

@@ -1,7 +1,7 @@
 import { reactive, watch } from 'vue'
 
 import type { ColorModeInstance } from './types'
-import { defineNuxtPlugin, isVue2, useRouter, useState } from '#imports'
+import { defineNuxtPlugin, isVue2, isVue3, useRouter, useState } from '#imports'
 import { globalName, storageKey, dataValue } from '#color-mode-options'
 
 const helper = window[globalName] as unknown as {