feat: add the makeObject option for Stringer

[vanyauhalin]

Hi Eugene! I just wanted to say that your library is awesome.

I've a request. Would it be possible for you to add the makeObject option for the Stringers since we already have the makeArray one? I've a situation where I need to process an array of elements into a map.

Thanks in advance!

[
  { "id": "first" },
  // ...
  { "id": "fifth" }
]

{
  "first": 0,
  // ...
  "fifth": 4
}

let i = 0

new Chain([
  createReadStream(from),
  parser(),
  new StreamArray(),
  new Transform({
    objectMode: true,
    transform(ch, _, cb) {
      pushPair.call(this, ch.value.id, i)
      i += 1
      cb(null)
    }
  }),
  new Transform({
    objectMode: true,
    transform(ch, enc, cb) {
      this.push({ name: "startObject" })
      this._transform = transformPassThrough
      return this._transform(ch, enc, cb)
    },
    flush(cb) {
      if (this._transform === transformPassThrough) {
        this.push({ name: "endObject" })
      }
      cb(null)
    }
  }),
  new Stringer(),
  createWriteStream(to)
])

function transformPassThrough(ch, enc, cb) {
  this.push(ch, enc)
  cb(null)
}