code: function contentDisposition (filename, options) {
    var opts = options || {}
  
    // get type
    var type = opts.type || 'attachment'
  
    // get parameters
    var params = createparams(filename, opts.fallback)
  
    // format into string
    return format(new ContentDisposition(type, params))
  }
docs: Create an attachment Content-Disposition header.
  
  @param {string} [filename]
  @param {object} [options]
  @param {string} [options.type=attachment]
  @param {string|boolean} [options.fallback=true]
  @return {string}
  @public