Fix TS types

[kibertoad]

fixes #304

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

[kibertoad]

@climba03003 Technically busboy types are correct, it does need that parameter for functioning. However, fastify-multipart types were wrong, because we were not relying on user to pass that parameter, we were retrieving it from request directly.

[kibertoad]

This part of busboy types was missing

[climba03003]

@climba03003 Technically busboy types are correct, it does need that parameter for functioning. However, fastify-multipart types were wrong, because we were not relying on user to pass that parameter, we were retrieving it from request directly.

I will use Omit<BusboyConfig, 'headers'> as we handle headers already.
Partial also allow the users to pass the headers which may lead to the same problem again.

[kibertoad]

@climba03003 Good point. Fixed.

[climba03003]

LGTM.

[rhadamez]

You guys are too fast, thats how a real framework should happen. Thanks.