feat: add img alt

[xrkffgg]

🤔 这个变动的性质是？/ What is the nature of this change?

• 新特性提交 / New feature
• bug 修复 / Fix bug
• 样式优化 / Style optimization
• 包体积优化 / Package size optimization
• 性能优化 / Performance optimization
• 代码风格优化 / Code style optimization
• 构建优化 / Build optimization
• 网站、文档、Demo 改进 / Website, documentation, demo improvements
• 测试相关 / Test related
• 其他 / Other

🔗 相关 Issue / Related Issue

💡 需求背景和解决方案 / Background or solution

📝 更新日志 / Changelog

Language	Changelog
🇺🇸 English	Add img alt
🇨🇳 Chinese	增加图片 alt 属性

☑️ 请求合并前的自查清单 / Self Check before Merge

⚠️ 请自检并全部勾选全部选项。⚠️
⚠️ Please check all items below before review. ⚠️

• 文档已补充或无须补充 / Doc is updated/provided or not needed
• 代码演示已提供或无须提供 / Demo is updated/provided or not needed
• TypeScript 定义已补充或无须补充 / TypeScript definition is updated/provided or not needed
• Changelog 已提供或无须提供 / Changelog is provided or not needed

[github-actions]

🎊 PR Preview a885bec has been successfully built and deployed to https://image-component-react-image-shadow-preview-pr-9.surge.sh

🕐 Build time: 165.336s

_{🤖 By surge-preview}

[github-actions]

Size Change: +30 B (1%)

Total Size: 2.1 kB

Filename	Size	Change
./dist/index.esm.js	887 B	+16 B (1%)
./dist/index.js	981 B	+14 B (1%)

ℹ️ View Unchanged

Filename	Size	Change
./dist/index.css	235 B	0 B

_{compressed-size-action}

[codecov]

Codecov Report

Merging #9 (a885bec) into main (5abd5a8) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##              main        #9   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines            8         8           
  Branches         4         4           
=========================================
  Hits             8         8           

Impacted Files	Coverage Δ
src/image-shadow.tsx	100.00% <ø> (ø)

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