code: public function setKey($key, $value = null, $comment = null, $export = false)
      {
          $data = [compact('key', 'value', 'comment', 'export')];
  
          return $this->setKeys($data);
      }
docs: Set one key to buffer
  
  @param string       $key      Key name of setter
  @param string|null  $value    Value of setter
  @param string|null  $comment  Comment of setter
  @param boolean      $export   Leading key name by "export "
  
  @return DotenvEditor