Integrate a link validation job

I'm unsure if we could introduce lychee to check links; it might have trouble with Hugo syntax links (eg, `{{< ref "/post/..." >}}`).

Maybe we could generate html from markdown and check the html, though it would make it hard to find where the bad link is used.

未指定文件、测试或入口点。首先检查此 Hugo 站点如何从 Markdown 生成 HTML，然后针对诸如 `{{< ref "/post/..." >}}` 这样的 Hugo 引用语法评估 lychee；当选定一种能够报告损坏链接及有用源位置的链接验证方法时，这项工作就完成了。

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