chore(image): demo代码风格优化

[Alex-huxiyang]

image一行展示固定个数 ==> image之间固定距离，自动排列换行，修正demo中的“文字未居中”

🤔 这个变动的性质是？

• [x] 站点、文档改进
• [x] 演示代码改进
• [x] 代码风格优化

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 85.85%. Comparing base (13ead53) to head (7c3f03e).

Additional details and impacted files

@@           Coverage Diff           @@
##             next    #2220   +/-   ##
=======================================
  Coverage   85.85%   85.85%           
=======================================
  Files         217      217           
  Lines       22841    22841           
  Branches     2480     2480           
=======================================
  Hits        19610    19610           
  Misses       3226     3226           
  Partials        5        5           

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