docs: add AchmadWahyu as a contributor for code, test

[allcontributors]

Add @AchmadWahyu as a contributor for code, test.

This was requested by zainfathoni in this comment

[vercel]

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🔍 Inspect: https://vercel.com/rumahberbagi/kelas/DbfgNatkQ3ztkEy573mFWvmUPoRx
✅ Preview: https://kelas-git-all-contributors-add-achmadwahyu-rumahberbagi.vercel.app

[codecov-commenter]

Codecov Report

Merging #169 (0d28418) into main (65d6da3) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #169   +/-   ##
=======================================
  Coverage   16.60%   16.60%           
=======================================
  Files          73       73           
  Lines        1036     1036           
  Branches      363      363           
=======================================
  Hits          172      172           
  Misses        862      862           
  Partials        2        2           

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