virtual-scroll: design interaction with find-in-page (ctrl+f)

Can we do anything to make it easier for users to implement replacement find-in-page (ctrl+f) that supports virtual-scroll. We can't detect native browser ctrl+f, but we may be able to make it easier for users who plan to implement their own ctrl+f replacement.

未指定文件、测试或入口点。首先阅读 virtual-scroll 组件及其公共 API，然后研究替代 find-in-page 实现如何与虚拟化内容交互。完成条件是形成一份经过共同认可并记录在案的设计或 API，使用户更容易进行这种交互。

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