code: function getHeader (header, field) {
    const re = new RegExp(`(?:\\r\\n)${field}: *([a-zA-z0-9 /,:;=-]*)`, 'gi')
    return re.exec(header, field)
  }
docs: @function
  @public
  
  Find value of header field in a stringified header.
  
  @param {Object} header The stringified header
  @param {string} field The header field to be searched for
  @returns {Array | null} The result of the executed RegExp