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/07-objects/answer.js

@@ -0,0 +1,12 @@
+const course = {
+  title: "JavaScript 核心",
+  lessons: 12,
+  finished: false,
+};
+
+course.finished = true;
+course.teacher = "周老师";
+
+console.log(course);
+console.log("课程名称：", course.title);
+console.log("授课老师：", course.teacher);