DOC add pca plot for data pruning example

[MatthewSZhang]

Checklist

• Used a personal fork to propose changes
• A reference to a related issue: DOC add PCA visualisation in data pruning example #65
• A description of the changes: Add PCA plot for data pruning example

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (84b2f83) to head (20c3780).
Report is 26 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #86   +/-   ##
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  Coverage   100.00%   100.00%           
=========================================
  Files            6         6           
  Lines          603       609    +6     
=========================================
+ Hits           603       609    +6     

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