docs: a demo use typescript

[xiaohuoni]

🤔 This is a ...

affix、alert、anchor、auto-complete、avatar 组件demo，使用 typescript 重写

• New feature
• Bug fix
• Site / document update
• Component style update
• TypeScript definition update
• Refactoring
• Code style optimization
• Test Case
• Branch merge
• Other (about what?)

🔗 Related issue link

💡 Background and solution

📝 Changelog

Language	Changelog
🇺🇸 English
🇨🇳 Chinese

☑️ Self Check before Merge

• Doc is updated/provided or not needed
• Demo is updated/provided or not needed
• TypeScript definition is updated/provided or not needed
• Changelog is provided or not needed

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View rendered components/affix/demo/on-change.md
View rendered components/alert/demo/banner.md
View rendered components/alert/demo/basic.md
View rendered components/alert/demo/closable.md
View rendered components/alert/demo/close-text.md
View rendered components/alert/demo/custom-icon.md
View rendered components/alert/demo/description.md
View rendered components/alert/demo/error-boundary.md
View rendered components/alert/demo/icon.md
View rendered components/alert/demo/smooth-closed.md
View rendered components/alert/demo/style.md
View rendered components/anchor/demo/basic.md
View rendered components/anchor/demo/customizeHighlight.md
View rendered components/anchor/demo/onChange.md
View rendered components/anchor/demo/onClick.md
View rendered components/anchor/demo/static.md
View rendered components/anchor/demo/targetOffset.md
View rendered components/auto-complete/demo/basic.md
View rendered components/auto-complete/demo/certain-category.md
View rendered components/auto-complete/demo/custom.md
View rendered components/auto-complete/demo/form-debug.md
View rendered components/auto-complete/demo/non-case-sensitive.md
View rendered components/auto-complete/demo/options.md
View rendered components/auto-complete/demo/uncertain-category.md
View rendered components/avatar/demo/badge.md
View rendered components/avatar/demo/basic.md
View rendered components/avatar/demo/dynamic.md
View rendered components/avatar/demo/toggle-debug.md
View rendered components/avatar/demo/type.md

[ant-design-bot]

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This pull request is automatically built and testable in CodeSandbox.

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[codecov]

Codecov Report

Merging #21045 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #21045   +/-   ##
=======================================
  Coverage   97.48%   97.48%           
=======================================
  Files         296      296           
  Lines        6910     6910           
  Branches     1917     1918    +1     
=======================================
  Hits         6736     6736           
  Misses        174      174

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[zombieJ]

import React from 'react'; is removable

[afc163]

尽量保留这个引用，这样和真实场景更接近。