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• Revise notebook content - is anything out of date?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 (can you think of any way to automate verifying this? would be useful to enforce in the test suite... downloading the colab version from the command line and running a diff would be possible, if you can find a way to do the download?)

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

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.88%. Comparing base (67cdb91) to head (129a5f2).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #18   +/-   ##
=======================================
  Coverage   92.88%   92.88%           
=======================================
  Files           6        6           
  Lines        1138     1138           
  Branches      203      203           
=======================================
  Hits         1057     1057           
  Misses         45       45           
  Partials       36       36           

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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...