chore: drop commitizen and tidy package metadata

[tarikjabiri]

Summary

Post-migration cleanup on next.

• Remove commitizen + cz-conventional-changelog, .czrc, and the now-dead commit script
• Remove leftover .eslintignore (eslint was replaced by biome)
• Remove unused @types/opentype.js (not referenced anywhere in src)
• Simplify files to "lib"
• Trim README (drop the Openbase badge and the Sponsors section)

Verified

• bun install --frozen-lockfile in sync ✓
• bun run build — all entries + IIFE emit, no missing opentype types ✓

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.44%. Comparing base (3139fc1) to head (cac3fc3).
⚠️ Report is 1 commits behind head on next.

Additional details and impacted files

@@           Coverage Diff           @@
##             next     #200   +/-   ##
=======================================
  Coverage   99.44%   99.44%           
=======================================
  Files          89       89           
  Lines        2337     2337           
  Branches      260      260           
=======================================
  Hits         2324     2324           
  Misses         13       13           

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