Add example describing the structure of the JSON/dict input format for Dataset object

[JulioAPeraza]

Add example describing the structure of the JSON/dict input format for Dataset object.

Closes #910.

Summary by Sourcery

Add an example describing the structure of the JSON/dict input format for the Dataset object.

New Features:

• Add a new example demonstrating how to create a Dataset object from a JSON file.

Documentation:

• Document the JSON/dict input format for the Dataset object.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.23%. Comparing base (0de67c5) to head (3e192e7).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #911   +/-   ##
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  Coverage   88.23%   88.23%           
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  Files          48       48           
  Lines        6382     6382           
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  Hits         5631     5631           
  Misses        751      751           

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[jdkent]

Thanks for doing this, this is a good contribution! I just changed the Study/Contrast level->dictionary since that describes the data type used at those levels and makes it consistent with the lower section headings.