update: use vue-demi again to add compatability to vue2

* add vite.config.app.ts for demo generation

src/shims-vue.d.ts

@@ -1,5 +1,5 @@
 declare module '*.vue' {
-  import { DefineComponent } from 'vue';
+  import { DefineComponent } from 'vue-demi';
   // eslint-disable-next-line @typescript-eslint/ban-types
   const component: DefineComponent<{}, {}, any>;
   export default component;