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-vue2/06-class-style-and-event/answer.js

@@ -0,0 +1,14 @@
+new Vue({
+  el: "#app",
+  data: {
+    title: "动态样式练习",
+    isActive: false,
+    progress: 35,
+  },
+  methods: {
+    toggleCard() {
+      this.isActive = !this.isActive;
+      this.progress = this.isActive ? 80 : 35;
+    },
+  },
+});