Include example HTML5 Drag and Drop API

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There is a chapter called [“Drag'n'Drop with mouse events”](https://javascript.info/mouse-drag-and-drop), and it makes a passing reference to the Drag and Drop API. There are plenty of cases where it’s appropriate to choose this approach.

However, I think there also needs to be a “Drag'n'Drop with the API” chapter.

I’ve been using the DND API on a learning project. Although I got over the strange hurdle of learning which events apply to draggable items and which events apply to drop zones, I’m at a point where I am really missing the awesome guidance I can find on most other topics in your excellent work.

For the purpose of inspiration in creating such a chapter (or for anyone else reading this), one tutorial I found helpful helpful is this video (which includes the basics of the DND API, and implements a list-sorting feature):

https://www.youtube.com/watch?v=jfYWwQrtzzY

阅读 https://javascript.info/mouse-drag-and-drop 上现有的“Drag'n'Drop with mouse events”章节，并查看所引用的教程视频，以评估其中对 HTML5 Drag and Drop API 的覆盖情况。完成标准是添加一个解释该 API 的新章节，其中包括 draggable-item 和 drop-zone 事件，并提供何时使用它的实践指导。

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