Diátaxis: Where are we?

There seems to be general consensus that diátaxis is a great theoretical model for structuring documentation.
However, using it – restructuring Python's docs – is a monumental task that needs some planning upfront.
@AA-Turner mentioned on the recent meeting that it would be good to start by charting the starting point: where on the Diátaxis chart do individual sections of the docs fall?
With that info we should be able to start planning where they should fall, and restructure/rewrite accordingly.

首先，查看 issue 中链接的 Diátaxis 模型以及 Python 文档的当前结构。盘点各个文档部分，并记录每一部分在 Diátaxis 图表中的归类位置；当这份起始地图可用于规划重构和重写时，工作即告完成。