收尾：refactor、tidy up

[wendyyuchensun]

1. 右欄 tooltip 不太好用：https://github.com/coseeing/Access8MathWeb/pull/129/changes#diff-5c940b3e659e90485d0d6f55e2336c022b70f7378a7ddac6ab5e30e0a93b52dcR39，a11y https://github.com/coseeing/Access8MathWeb/pull/129/changes#diff-5c940b3e659e90485d0d6f55e2336c022b70f7378a7ddac6ab5e30e0a93b52dcR39Add tabIndex={0} to the tooltip trigger span so keyboard users can access the alt-text tooltip.
   preview 顏色對比度
   preview 如果超出頁面位置
   考慮 image 位置
   preview 影響其他 aria describedby
   https://www.joshwcomeau.com/css/anchor-positioning/

2. a11y audit, e.g. 放大 200%, image modal file input error live region 似乎不太穩定

3. seemark: feat: support http(s) URLs as image sources across image extensions SeeMark#37 (comment)

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3. external link aria describededby 3af6870

4. 右欄 darkmode 可否用 tailwind 處理？

module.exports = {    darkMode: ['variant', '.right-side-preview-area.darkmode &'],
    content: ['./src/**/*.{js,jsx,ts,tsx}'],
    // ...
  }

9. 連動匯出的 template 是否要更新 CSS？

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12. review code & refactor
13. 頁面捲到最下方時，覺得 editoral render 似乎 render 效能不好
14. refactor：e.g. tailwind 4 的倍數, feat: support http(s) URLs as image sources across image extensions SeeMark#37 (comment)