feat: export httpErrors

[arthurfiorette]

These errors already can be used with fastify.httpErrors, however, when writing util functions or functions that will endup inside a route call but are elsewhere, passing the fastify.httpErrors as parameters throughout multiple functions is bad. It is already exported from lib/httpErrors, this PR just add their types and the index.js httpErrors export.

Test for types and js were added.

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[arthurfiorette]

Ready for review :)

[Uzlopak]

LGTM