Revert "chore: remove vueuse"

This reverts commit ccc82f5e0e.

src/runtime/plugin.ts

@@ -0,0 +1,6 @@
+import { useDark } from '@vueuse/core'
+import { defineNuxtPlugin } from '#app'
+
+export default defineNuxtPlugin(() => {
+  useDark()
+})