docs: 添加怀旧风格的样式自定义示例

[yutingzhao1991]

添加了一个更复杂的自定义样式，体现出 Ant Design 和 Ant Design Web3 自定义样式的能力：

[changeset-bot]

🦋 Changeset detected

Latest commit: e55c770

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 4 packages

Name	Type
@ant-design/web3	Patch
@example/eth-web3js	Patch
@example/ethers-v5	Patch
@example/ethers	Patch

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Name	Status	Preview	Comments	Updated (UTC)
ant-design-web3	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Feb 12, 2025 9:25am

[github-actions]

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.99%. Comparing base (f896044) to head (e55c770).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1344   +/-   ##
=======================================
  Coverage   99.99%   99.99%           
=======================================
  Files         861      861           
  Lines       14850    14851    +1     
  Branches     1621     1628    +7     
=======================================
+ Hits        14849    14850    +1     
  Misses          1        1           

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