Restore experiments link?

I'm a little sad that the experiments are no longer linked from the main navbar, and I don't think they're linked from anywhere else. You can still navigate to /experiments if you remember the URL, but could we get a link to it back? Or is there a grander plan here?

从主导航栏开始，检查现有的 /experiments 入口。恢复一个指向 /experiments 的可见导航链接，然后验证它会显示在导航栏中并能进入 experiments 页面。

由索引模型根据 Issue 内容生成。