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-vue3/09-reactivity-helpers/starter.js

@@ -0,0 +1,33 @@
+const { createApp, reactive, toRef, toRefs, readonly } = Vue;
+
+createApp({
+  setup() {
+    const profile = reactive({
+      name: "林晨",
+      stage: "Vue3 入门",
+      studyDays: 12,
+    });
+
+    const name = toRef(profile, "name");
+    const { stage, studyDays } = toRefs(profile);
+    const settings = readonly({
+      theme: "light",
+    });
+
+    function updateProfile() {
+      // 任务：
+      // 1. 更新 name.value
+      // 2. 更新 stage.value
+      // 3. 让 studyDays.value + 1
+      // 4. 不要直接修改 settings.theme
+    }
+
+    return {
+      name,
+      stage,
+      studyDays,
+      settings,
+      updateProfile,
+    };
+  },
+}).mount("#app");