chore: 接入 ESLint 并修复存量错误

src/main.ts

@@ -7,7 +7,7 @@ import App from './App.vue'
 import router from "@/router"
 import 'normalize.css'
 
-var app = createApp(App)
+const app = createApp(App)
 app.use(ElementPlus)
 app.use(router)
 app.mount('#app')