feat: Add JavaScript core exercises and solutions

- Implemented exercises for array high-order methods, memory and execution, switch statements, and final review.
- Added starter and answer files for each exercise to facilitate learning.
- Created a runner HTML file to execute JavaScript code and display console outputs.
- Updated README files to include exercise objectives, tasks, and usage instructions.

03-javascript-core/13-array-high-order-methods/starter.js

@@ -0,0 +1,14 @@
+const scores = [58, 76, 91, 84];
+const students = [
+  { name: "小周", finished: true },
+  { name: "小林", finished: true },
+  { name: "小陈", finished: false },
+];
+
+// 任务：
+// 1. 用 map 生成 ["58分", ...]
+// 2. 用 filter 筛出及格分
+// 3. 用 reduce 计算总分
+// 4. 用 find 找到第一个 >= 90 的分数
+// 5. 用 some 判断是否存在不及格
+// 6. 用 every 判断 students 是否都 finished 为 true