feat: export ScanStream at package level (#667)

Author: Yamil Asusta

lib/index.js

@@ -5,6 +5,7 @@ exports = module.exports = require('./redis');
 exports.ReplyError = require('redis-errors').ReplyError;
 exports.Cluster = require('./cluster');
 exports.Command = require('./command');
+exports.ScanStream = require('./ScanStream').default;
 
 var PromiseContainer = require('./promiseContainer');
 Object.defineProperty(exports, 'Promise', {