feat: Add CSS layout exercises and corresponding HTML files

- Created multiple exercises under the CSS layout section, including:
  - Final page layout with CSS styles and HTML structure.
  - Display and flow concepts with examples of block, inline, and none display types.
  - Selectors and pseudo-classes with practical examples.
  - Overflow and sizing handling in CSS.
  - Grid layout basics for two-dimensional layouts.
  - Fixed and sticky positioning examples.
  - Centering techniques for common layout scenarios.

- Added README files for each exercise to outline objectives and file structures.
- Updated main README to include new sections and usage instructions.

01-html-structure/07-media-and-paths/README.md

@@ -0,0 +1,29 @@
+# 练习 7：图片、视频与路径
+
+## 目标
+
+掌握媒体标签和资源路径的基础写法。
+
+## 你要练什么
+
+- `img`
+- `video`
+- `src`
+- `alt`
+- `controls`
+
+## 任务
+
+请完成一个“课程展示页”，要求包含：
+
+- 一个课程封面图
+- 一段图片说明
+- 一个视频区域
+- 一个下载讲义链接
+
+资源文件可以先用占位路径，不要求真实可播放。
+
+## 文件
+
+- [starter.html](/Volumes/Macintosh HD 1/home/front-end-example/01-html-structure/07-media-and-paths/starter.html)
+- [answer.html](/Volumes/Macintosh HD 1/home/front-end-example/01-html-structure/07-media-and-paths/answer.html)