Revamp of the Intro Notebooks

[kjdoore]

This is a major update to the introductory (101) notebooks. It breaks the contents down into five parts:

1. Introduction to chunking overall with toy example
2. How to read existing data sets and determine their chunking
3. Basics on selecting chunk shape and size
4. How to write chunked data to zarr
5. How to rechunk existing data using rechunker

I was thinking that these notebooks cover the basics to help someone understand chunking and how to perform it in a basic way. Other more complex topics (rechunking on the cloud, optimizing chunk shape, etc) would be placed in a different "Advanced Topics" (201) section of this juypter book.
Let me know your thoughts and if you think I may have missed a topic you would consider "introductory" to chunking.

[kjdoore]

To view the notebooks in a JupyterBook view, first switch to the kjdoore-updates branch. You will then create the conda environment from the env.yml file:

conda env create -f env.yml
conda activate chunking

The book can then be created with

jupyter-book build ./

To view the book, open the following file: _build/html/index.html

[kjdoore]

@amsnyder these should be the last updates. Should be ready for a review