socket.io redis 如何配置 集群 以及Sentinel 模式
## What happens?
A clear and concise description of what the bug is.

## Mini Showcase Repository(REQUIRED)
> Provide a mini GitHub repository which can reproduce the issue.
> Use `npm init egg --type=simple bug` then upload to your GitHub

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## How To Reproduce

**Steps to reproduce the behavior:**
1.现在只能配置单例


**Expected behavior**
1.可以在socketio里配置redis 集群
2.可以配置哨兵模式

## Context
- **Node Version**:12.18.1
- **Egg Version**:2.15.1
- **Plugin Name**:egg-scoket.io
- **Plugin Version**:4.1.6
- **Platform**:
