refactor: redesign module system

src/modules/nprogress.ts

@@ -0,0 +1,9 @@
+import NProgress from 'nprogress'
+import { UserModule } from '/~/types'
+
+export const install: UserModule = ({ isClient, router }) => {
+  if (isClient) {
+    router.beforeEach(() => { NProgress.start() })
+    router.afterEach(() => { NProgress.done() })
+  }
+}