fix: add missing defineNuxtPlugin import

Author: pi0

src/runtime/plugin.ts

@@ -1,5 +1,6 @@
 import { createImage } from '#image'
 import { imageOptions } from '#build/image-options'
+import { defineNuxtPlugin } from '#imports'
 
 export default defineNuxtPlugin(() => {
   const img = createImage(imageOptions)