fix: ensure Plugin type isn't stripped in build (#478)

Author: LouisHaftmann

src/runtime/router.ts

@@ -11,7 +11,8 @@ import type { RouteLocation, Router } from 'vue-router'
 import { createError } from 'h3'
 import { withoutBase, isEqual } from 'ufo'
 
-import type { PageMeta, RouteMiddleware, Plugin } from '#app'
+import type { PageMeta, RouteMiddleware } from '#app'
+import type { Plugin } from 'nuxt/app'
 import { callWithNuxt, defineNuxtPlugin, useRuntimeConfig } from '#app/nuxt'
 import { showError, clearError, useError } from '#app/composables/error'
 import { useRequestEvent } from '#app/composables/ssr'