refactor: migrate demo applications to playground (#4116)

* chore: detail adjustment

* refactor: Migrate demo applications to playground

* perf: logic optimization

* chore: update docs

* chore: update docs

playground/src/layouts/index.ts

@@ -0,0 +1,8 @@
+const BasicLayout = () => import('./basic.vue');
+
+const IFrameView = () => import('@vben/layouts').then((m) => m.IFrameView);
+
+const AuthPageLayout = () =>
+  import('@vben/layouts').then((m) => m.AuthPageLayout);
+
+export { AuthPageLayout, BasicLayout, IFrameView };