No option to init new watcher (clustered) with redis client

[yashzod]

Currently, there is no way to initialize a new watcher (in clustered mode) using an existing Redis client instance. The code expects Redis connection details like host, port, or options to internally create a new Redis client.

In my use case, I already have an active Redis client (due to restricted access to connection details or centralized Redis setup), and I need to reuse this client to create a clustered watcher.

[kuchaguangjie]

I also need this.

[yashzod]

https://github.com/casbin/redis-watcher/pull/52/files
I have raised a PR. I hope this helps.