docs: add conrmahr as a contributor for code

[allcontributors]

Adds @conrmahr as a contributor for code.

This was requested by JoshuaKGoldberg in this comment

[JoshuaKGoldberg]

Lol @conrmahr looks like I might have been wrong about the .all-contributorsrc file being prettified automatically...

[codecov]

Codecov Report

Merging #808 (e83c242) into main (8dbde91) will not change coverage.
Report is 1 commits behind head on main.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #808   +/-   ##
=======================================
  Coverage   91.60%   91.60%           
=======================================
  Files          84       84           
  Lines        4158     4158           
  Branches      248      248           
=======================================
  Hits         3809     3809           
  Misses        349      349           

Flag	Coverage Δ
create	72.01% <ø> (ø)
initialize	34.03% <ø> (ø)
migrate	73.33% <ø> (ø)
unit	47.66% <ø> (ø)

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[conrmahr]

@JoshuaKGoldberg I'm seeing GitHub Actions handling the array format differently then locally with the .all-contributorsrc.

GitHub

      "contributions": [
        "code"
      ]

Locally

      "contributions": [ "code"]

[JoshuaKGoldberg]

I'll do this manually.