Add new notebook for diagnostic tools

It'll be useful to have a dedicated notebook to discuss Dask's diagnostic tools, including task graph visualization, widgets for local compute, dashboard for distributed computation, etc. It can be a subset of https://docs.dask.org/en/stable/understanding-performance.html

@charlesbluca, @ncclementi, and I are submitting a Dask proposal for PyData Global 2022, and we plan to add this notebook as a part of our prep.

首先阅读 docs.dask.org/en/stable/understanding-performance.html 中链接的 Dask 性能文档，并确定适合用于专用 notebook 的内容。该 notebook 应涵盖任务图可视化、本地计算小部件和分布式 dashboard，同时保持为该指南的一个子集。确认最终得到的 notebook 支持为拟议的 PyData Global 2022 做准备。

由索引模型根据 Issue 内容生成。