docs: add markehvn as a contributor for tool

[allcontributors]

Adds @markEHVN as a contributor for tool.

This was requested by JoshuaKGoldberg in this comment

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.50%. Comparing base (7051abb) to head (09644f8).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #364   +/-   ##
=======================================
  Coverage   95.50%   95.50%           
=======================================
  Files          11       11           
  Lines         334      334           
  Branches       42       42           
=======================================
  Hits          319      319           
  Misses         15       15           

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