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

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

vite.config.ts

@@ -13,12 +13,12 @@ export default defineConfig({
     rollupOptions: {
       // make sure to externalize deps that shouldn't be bundled
       // into your library
-      external: ['vue'],
+      external: ['vue-demi'],
       output: {
         // Provide global variables to use in the UMD build
         // for externalized deps
         globals: {
-          'vue': 'Vue'
+          'vue-demi': 'VueDemi'
         },
         dir: 'dist',
         sourcemap: true,
@@ -28,7 +28,7 @@ export default defineConfig({
     }
   },
   optimizeDeps: {
-    exclude: ['vue']
+    exclude: ['vue-demi']
   },
   plugins: [
     vue(),