RateLimiterCluster with PM2 cluster mode and Redis as store client
Hi there. First, thank you for the excellent library!

I'm having an issue when attemping to implement the RateLimiterCluster with PM2 in cluster mode.

I followed the example you wrote here: 
https://github.com/animir/node-rate-limiter-flexible/wiki/PM2-cluster

However your example doesn't include a 'storeClient' prop passed to the `RateLimiterCluster ` constructor (even though the TS definitions have `IRateLimiterStoreOptions` as the options interface accepted by `RateLimiterCluster`). So I add the `storeClient` prop anyway, which points to my `redisClient` (node-redis), and fire everything up.

It seems as if my redis store isn't being touched at all, even though the rate limiting is working. This suggests to me that even though I specified my `redisClient` as the `storeClient`, `RateLimiterCluster` is actually operating in-memory.

Can you tell me how to hook `RateLimiterCluster` to my redis store? Or perhaps it actually should be in-memory only? And if that's the case, can you change the interface required by the `RateLimiterCluster` constructor to exclude the `storeClient` prop?

Thanks very much!