Include example HTML5 Drag and Drop API

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

Read the existing “Drag'n'Drop with mouse events” chapter at https://javascript.info/mouse-drag-and-drop and review the referenced tutorial video for HTML5 Drag and Drop API coverage. Done means adding a new chapter that explains the API, including draggable-item and drop-zone events, and gives practical guidance on when to use it.

Written by the indexing model from the issue text.