[Feature Request] 是否有designable的详细文档

[gtrgeg]

• [ ] I have searched the issues of this repository and believe that this is not a duplicate.

What problem does this feature solve?

表单设计器开发指南写的太简单了点，是否有文档，readme或者站点之类的东西能大致讲解一下designable源代码的设计和各个API

What does the proposed API look like?

出一个designable源代码的文档，包括结构设计和各模块功能的讲解