title: WinstonJS custom level to file
body: <p>I changed the default levels in Winston.JS, to remove 2 levels and add 1 custom level. I want to log that new level in an separated file. So that file will only contains logs from that level.</p>
  
  <pre><code>const appRoot = require('app-root-path');
  const winston = require('winston');
  require('winston-daily-rotate-file');
  
  const levels = {
      levels: {
          product: 0,
          error: 1,
          warn: 2,
          info: 3,
          debug: 4,
          product: 5,
      },
      colors: {
          product: 'magenta',
          error: 'red',
          warning: 'yellow',
          info: 'green',
          debug: 'blue',
      }
  }
  
  const logger = winston.createLogger({
      levels: levels.levels,
      format: winston.format.combine(
          winston.format.colorize(),
          winston.format.timestamp({
              format: 'DD-MM-YYYY HH:mm:ss'
          }),
          winston.format.printf(info =&gt; `[${info.timestamp}] [${info.level}]: ${info.message}`)
      ),
      transports: [
          new winston.transports.DailyRotateFile({
              filename: `${appRoot}/logs/error-%DATE%.log`,
              level: 'error', 
              datePattern: 'YYYY-MM-DD',
              maxSize: '20m',
              maxFiles: '14d'
          }),
          new winston.transports.DailyRotateFile({
              filename: `${appRoot}/logs/product-%DATE%.log`,
              level: 'product',
              datePattern: 'YYYY-MM-DD',
              maxSize: '20m',
              maxFiles: '14d' 
          })
      ]
  })
  winston.addColors(levels.colors);
  
  logger.stream = {
      write: (message, encoding) =&gt; {
          logger.info(message);
      }
  }
  </code></pre>
  
  <p>In this case, I want to place all the <code>console.product()</code> logs in the <code>product-%DATE%.log</code> file. 
  Currently the file is filled, but only with the information which is also showed in the log about from express (<code>app.use(morgan("combined", {stream: winston.stream}));</code>)
  In development I also adding an extra transport for debug on the console:</p>
  
  <pre><code>let env = process.env.NODE_ENV;
  
  if (env !== 'production'){
      logger.add(new winston.transports.Console({
          level: 'debug',
          prettyPrint: function ( object ){
              return JSON.stringify(object);
          }
      }))
  }
  </code></pre>
  
  <p>How can I get only the <code>console.product()</code> logs into the product.log file?</p>