[FEATURE REQUEST] redis sentinel support

**Describe the solution you'd like**
not sure how to use sentinel with go-redis in iris.

[connect function](https://github.com/kataras/iris/blob/main/sessions/sessiondb/redis/driver_goredis.go#L125) seems only to support cluster and standalone redis:
```
// Connect initializes the redis client.
func (r *GoRedisDriver) Connect(c Config) error {
if r.Client != nil { // if a custom one was given through SetClient.
return nil
}

if len(c.Clusters) > 0 {
r.Client = redis.NewClusterClient(r.mergeClusterOptions(c))
} else {
r.Client = redis.NewClient(r.mergeClientOptions(c))
}

return nil
}
```