async-redis: Add export interface

redis.ts

// For example, I use Dependency Injection pattern in my architecture of node.js app

import asyncRedis from 'async-redis'
import { Container } from 'typedi'

const client = asyncRedis.createClient(config.redis)

Container.set('redis', client)

service-a.ts

import { Service, Inject } from 'typedi'

@Service()
export default class Animal {
  constructor (
    @Inject('redis') private redis: any // <-- problem here, i can't set type of redis client
  ) {}

  async getAll () {
    // this.redis is any and set-method is too any
    await this.redis.set('foo', 'bar')
  }
}

service-b.ts

// What I expecting

import { Service, Inject } from 'typedi'
import { Promisified, RedisClient } from 'async-redis'

@Service()
export default class Animal {
  constructor (
    @Inject('redis') private redis: Promisified<RedisClient> // <-- here i can validate type-chicking
  ) {}

  async getAll () {
    await this.redis.set('foo', 'bar')
  }
}