feat(function): add decimal place to get_summary_statistics func

[jessiezhang24]

add decimal place argument to the mean calculation in get_summary_statistics() function
add test cases to validate decimal places rounding
update example usage to reflect function change
update docstring and readme to reflect function change

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (5892a8d) to head (2af3c87).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #47   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files            4         4           
  Lines           34        34           
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  Hits            34        34           

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