How to use the browserify.plugin function in browserify

browserify.transform(lessify,
  { // less options
    global: true,
  }
);

browserify.transform(
  envify({
    NODE_ENV: prod ? 'production' : 'development',
  }),
  { global: true }
);

if (watch) {
  var watchify = require('watchify');
  browserify.plugin(watchify,
    { // watchify options
      verbose: true,
      poll: 1000,
      ignoreWatch: '**/node_modules/**',
    }
  );

  infoLog('Starting watcher');

  browserify.on('update', function (ids) {
    infoLog('files changed, bundle updated');
    _.each(ids, function(id) {infoLog(id + ' changed');});
    createBundles(browserify, bundles);
  });

  browserify.on('log', infoLog);

exports.browserify = function (files) {
  console.error('You are setting up proxyquireify via the old API which will be deprecated in future versions.');
  console.error('It is recommended to use it as a browserify-plugin instead - see the example in the README.');
  return require('browserify')(files).plugin(plugin);
};