feat: add Vue2 exercises for dynamic styles, lifecycle methods, component communication, and course management dashboard

- Implement dynamic styles and event handling in Vue2 with a card component.
- Create lifecycle methods exercise to simulate async data loading and instance destruction.
- Develop a component communication exercise with props, events, and slots.
- Build a comprehensive course management dashboard with filtering, statistics, and component interactions.

07-vue2/07-lifecycle-and-async/starter.js

@@ -0,0 +1,30 @@
+new Vue({
+  el: "#app",
+  data: {
+    loading: true,
+    courses: [],
+  },
+  created() {
+    console.log("created: 实例已经创建");
+  },
+  mounted() {
+    // 任务：
+    // 1. 模拟异步请求
+    // 2. 1 秒后给 courses 赋值
+    // 3. loading 改成 false
+  },
+  updated() {
+    // 任务：在控制台输出 updated 日志
+  },
+  beforeDestroy() {
+    // 任务：在控制台输出 beforeDestroy 日志
+  },
+  destroyed() {
+    // 任务：在控制台输出 destroyed 日志
+  },
+  methods: {
+    destroyInstance() {
+      // 任务：调用 this.$destroy()
+    },
+  },
+});