suggestion for the first example in Render Props section

Currently the first example we see reads:

<DataProvider render={data => (
  <h1>Hello {data.target}</h1>
)}/>

Why not extend this initial example further and show what a DataProvider component might look like?
e.g. something like...

const DataProvider = props => {
  const data = {
    target: "World"
  }
  return props.render(data);
}

Granted, this is a fairly dumb example and not something you'd use a render prop for, but a dumb example might help solidify the basic concept before leading into more useful examples and conversations. Thoughts?

打开“Render Props”部分，并结合 issue 中提议的 DataProvider 示例，检查其中的第一个示例。更新介绍性示例，使 provider 实现与 render prop 之间的关系更加清晰；在后续示例之前就能理解基本概念时即完成。