Use temporary files in manual examples

[Joseph-Edwards]

This PR updates some manual examples so that they no longer create files in the current directory or the digraphs directory. Instead, it creates temporary files with DirectoryTemporary.

Thank you to @William-Kenyon for highlighting this issue!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.46%. Comparing base (c4ced48) to head (6d4a716).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #953   +/-   ##
=======================================
  Coverage   97.46%   97.46%           
=======================================
  Files          51       51           
  Lines       21191    21191           
  Branches      639      639           
=======================================
  Hits        20653    20653           
  Misses        473      473           
  Partials       65       65           

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[james-d-mitchell]

Thanks @Joseph-Edwards