Reconciliation docs need amendment

I think it can be clarified that the component that's rendering a React element of a new type will itself not be remounted; however, its child elements will be.

In other words if a component's render method returns

<div>
  <Counter />
</div>

when it is mounted and later (when it is updated)

<span>
  <Counter />
</span>

that component itself will not be remounted, but the <Counter/> element will be.

首先定位 issue 中讨论的 reconciliation 文档部分，并查看其中关于更改渲染元素类型的说明。明确渲染组件不会被重新挂载，而其子元素会被重新挂载，并使用 div/span 示例作为验收检查。