refactor!: new implementation

[climba03003]

Fixes #15

There is problem I faced in handling 304, Node.js will filled with un-wanted headers.
So, the test need to remove some assertion on the removal of headers.

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

[gurgunday]

Thanks for this!

It lgtm overall

[climba03003]

I am thinking do we need to provide similar utilities like the current .pipe.
It would be as simple as the below code for 304 case.

function pipe(send, res) {
  switch(send.statusCode) {
    case 304: {
      // remove Content-* headers
      res.removeHeader('Content-Encoding')
      res.removeHeader('Content-Language')
      res.removeHeader('Content-Length')
      res.removeHeader('Content-Range')
      res.removeHeader('Content-Type')
      break
    }
  }
  res.writeHead(send.statusCode, send.headers)
  send.stream.pipe(res)
}

[Uzlopak]

We can now remove http-errors as dependency :)

[mcollina]

lgtm

[Uzlopak]

Remove http-errors as dependency ;)

[Uzlopak]

LGTM

[gurgunday]

@climba03003 do you have time to refactor @fastify/static?