Is it possible to support an overall introduction page for the documentation?

[tianmingxing]

Summary(关于这个pr的描述)

Besides detailed explanations of the interfaces, weBesides detailed explanations of the interfaces, we related instructions, such as the such as the domain name for requesting interfaces, points to note when calling them, handling of some common issues, etc. All these need a page for clarification.

除了接口详细说明外，还需要记录一些相关的说明，例如：请求接口的域名，调用的注意事项，一些常见问题的处理等等。这些都需要有一个页面来进行说明。

Basic example(pr的用例)

1）It would be great if we could specify the relative path of this custom page in the configuration file, and the documentation can be in markdown format（可以在配置文件中指定这个自定义页面的相对路径，文档可以是markdown格式）
2）When generating, these pages should be rendered into the main documentation（在生成时将这些页面渲染到主文档中。）

Motivation(提出这个pr目的)

Some common information related to the interfaces needs to be documented.
需要记录一些和接口有关的公共信息

[luniard]

I strongly suggest updating this.
强烈建议更新下这个