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/06-block-and-inline/README.md

@@ -0,0 +1,28 @@
+# 练习 6：块级与行内元素
+
+## 目标
+
+分清什么标签默认独占一行，什么标签默认跟着文字流动。
+
+## 你要练什么
+
+- 块级元素
+- 行内元素
+- `div`
+- `span`
+- `p`
+- `a`
+- `strong`
+
+## 任务
+
+完成一个“学习提示条”，要求：
+
+- 用块级元素搭出 3 条提示
+- 每条提示中有关键词，用行内标签包起来
+- 不要把段落错误地放进行内标签里
+
+## 文件
+
+- [starter.html](/Volumes/Macintosh HD 1/home/front-end-example/01-html-structure/06-block-and-inline/starter.html)
+- [answer.html](/Volumes/Macintosh HD 1/home/front-end-example/01-html-structure/06-block-and-inline/answer.html)