Add CoLab example

[AleKit]

Include Kyle's CoLab SWIFTGalaxy demo Jupyter Notebook.
closes #10

AleKit:

• Add the .ipynb file into the examples/ directory as a"cleanly run" copy
• Link at the top of the notebook to the interactive version on CoLab
• Revise notebook content - is anything out of date?
• Fix warning(s) in notebook run.
• Make sure colab version and github version agree. Through pure sorcery, you can substitute github.com with githubtocolab.com in the notebook URL on the repo and it magically opens in colab!

kyleaoman:

• Add a README.rst file to the examples/ directory
• Direct users to the example directory in general (it's newly added) and to this basic example specifically in a few places: the main README.rst of the repository, and maybe one or two places in the docs hosted on RTD (think about suitable location(s))
• Add automated testing of this notebook to the github checks with the nbmake package. Add nbmake to the optional_requirements.txt file
• Use new interface to example data generator functions in notebook.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.92%. Comparing base (c59d323) to head (549f8b1).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #18      +/-   ##
==========================================
+ Coverage   95.71%   95.92%   +0.20%     
==========================================
  Files           7        7              
  Lines        2216     2232      +16     
  Branches      257      257              
==========================================
+ Hits         2121     2141      +20     
+ Misses         49       48       -1     
+ Partials       46       43       -3     

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[kyleaoman]

@AleKit it seems that you'd already done the items on your checklist months ago! I added a couple of other things that perhaps you could take care of?

I also merged in the latest changes from the main branch. and started on my part of the checklist a bit...