feat: scaffold merged miniapp shell

miniprogram/src/main.js

@@ -0,0 +1,15 @@
+import { createSSRApp } from 'vue'
+import App from './App.vue'
+import * as Pinia from 'pinia'
+import uviewPlus from 'uview-plus'
+import 'uview-plus/index.scss'
+
+export function createApp() {
+  const app = createSSRApp(App)
+  app.use(Pinia.createPinia())
+  app.use(uviewPlus)
+  return {
+    app,
+    Pinia
+  }
+}