feat: Add Vue3 exercises and interview plan

- Introduced Vue3 exercises covering composable API, reactivity, lifecycle hooks, and built-in components.
- Added structured interview plan for frontend candidates focusing on HTML, CSS, JavaScript, TypeScript, and Vue.
- Included starter files for each exercise and detailed README documentation for guidance.

08-vue3/07-composable-and-async/README.md

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+# 练习 7：composable 和异步状态
+
+## 目标
+
+学会把可复用逻辑抽成 composable，并管理 loading / error / data。
+
+## 你要练什么
+
+- composable
+- `ref`
+- 异步状态
+- `loading`
+- `error`
+
+## 任务
+
+- 把课程请求逻辑抽成 `useCourses`
+- 页面加载时调用它
+- 显示 loading
+- 请求成功后渲染列表
+- 请求失败时显示错误信息
+
+## 文件
+
+- [starter.html](/Users/lijiaqing/home/wwwroot/front-end-example/08-vue3/07-composable-and-async/starter.html)
+- [starter.js](/Users/lijiaqing/home/wwwroot/front-end-example/08-vue3/07-composable-and-async/starter.js)