fix: use repository name in README.md npm package badge

[JoshuaKGoldberg]

PR Checklist

• Addresses an existing open issue: fixes 🐛 Bug: Created npm package version badge in README.md uses wrong package name #1108
• That issue was marked as status: accepting prs
• Steps in CONTRIBUTING.md were taken

Overview

Replaces the hardcoded create-typescript-app name with options.repository. Also adds non-blank strings to unit tests so the snapshots will reflect this.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (127108f) 94.25% compared to head (60396ab) 94.25%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1109   +/-   ##
=======================================
  Coverage   94.25%   94.25%           
=======================================
  Files          97       97           
  Lines        5625     5625           
  Branches      454      454           
=======================================
  Hits         5302     5302           
  Misses        322      322           
  Partials        1        1           

Flag	Coverage Δ
create	70.21% <100.00%> (ø)
initialize	42.15% <0.00%> (ø)
migrate	69.55% <100.00%> (ø)
unit	72.31% <100.00%> (ø)

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[github-actions]

🎉 This is included in version v1.49.4 🎉

The release is available on:

• GitHub releases
• npm package (@latest dist-tag)

Cheers! 📦🚀