code: func NewEncoder(defaultEncoding Encoding, encodings ...Encoding) *Encoder {
  	m := make(map[Encoding]*mimeInfo)
  
  	for _, e := range append(encodings, defaultEncoding) {
  		info := parseMimeInfo(e.Mime())
  		m[e] = info
  	}
  
  	return &Encoder{
  		defaultEncoding: defaultEncoding,
  		encodings:       m,
  	}
  }
docs: // NewEncoder creates encoder