I hope the screen reader software doesn't read 'link' when it reads the title

## Feature request

I hope to add a feature that the md file title does not read out the link.

#### What problem does this feature solve?

Friendly for some people who use screen reader software

#### What does the proposed API look like?

just like

```
window.$docsify = {
readLink: false,
}
```

#### How should this be implemented in your opinion?

I don't think this should be hard to implement, e.g. generating html for md files without a tag.

I'm afraid I can't.

Issue 中没有提到文件或测试。首先跟踪 Markdown 标题如何变成 HTML，以及如何读取 window.$docsify 选项；当已配置的标题行为不再导致屏幕阅读器将其读作链接，同时保留现有的标题导航时，即表示完成。

由索引模型根据 Issue 内容生成。