Cite publications for software packages etc wherever possible

[brian-rose]

Foundations should model good scholarly practice and cite each resource or python package in ways consistent with what their authors recommend.

For example, here's the recommended citation for Numpy:
https://numpy.org/citing-numpy/

Related to #424, MyST makes it very easy to drop in a DOI and have a chapter-level "references" section appear automatically.

[brian-rose]

Mostly addressed in #548

[bl-freeman]

PR #548 added citations throughout the core packages portion of Foundations related to NumPy, Matplotlib, Cartopy, Pandas, and Xarray. No citations have been added for the foundational skills or for products without a strict (read: easy to find on a quick Google search) citation method or format. Future PRs will be created to address these changes.

Examples of citations still needed to address this issue (non-exhaustive):

• Jupyter products
• Unidata products (e.g. netCDF)
• Anaconda