fix: add missing cjs entry in package

[frantic1048]

Follow up #3963, fixes the missing cjs entry for @commitlint/cz-commitlint

#3963 (comment)

[codesandbox-ci]

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[frantic1048]

The package is ok for CJS consumer now, tested on local repo. cc @JounQin @escapedcat

ref: https://ci.codesandbox.io/status/conventional-changelog/commitlint/pr/3967/builds/482129

npm notice package: @commitlint/[email protected]
npm notice === Tarball Contents === 
npm notice 1.6kB README.md                                  
npm notice 164B  index.cjs                                  
npm notice 464B  lib/index.d.ts                             
npm notice 372B  lib/index.d.ts.map                         
npm notice 451B  lib/index.js                               
npm notice 407B  lib/index.js.map                           
npm notice 335B  lib/Process.d.ts                           
npm notice 390B  lib/Process.d.ts.map                       
npm notice 948B  lib/Process.js                             

[escapedcat]

https://github.com/conventional-changelog/commitlint/releases/tag/v19.1.0