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

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

vite.config.app.ts

@@ -0,0 +1,16 @@
+import { defineConfig } from 'vite';
+import vue from '@vitejs/plugin-vue';
+import vueJsx from '@vitejs/plugin-vue-jsx';
+
+// https://vitejs.dev/config/
+export default defineConfig({
+  build: {
+    outDir: 'build'
+  },
+  plugins: [
+    vue(),
+    vueJsx({
+      // options are passed on to @vue/babel-plugin-jsx
+    })
+  ]
+});