docs: add unocss usage

[9aoy]

Summary

fix: #654

Related Links

Checklist

• I have added changeset via pnpm run change.
• I have updated the documentation.
• I have added tests to cover my changes.

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[xmsz-stu]

有人试过新版本吗，现在只有unocss 0.58.9 @unocss/postcss 0.61.9 可以跑起来，其他会报错

File: /Users/chenshijian/code/cool-qi/apps/smart-response/src/global.css:1:1
  × Module build failed:
  ╰─▶   × Error: EISDIR: illegal operation on a directory, read