Release v4.0.0-beta.8

What's Changed

• Split status manager from client by @huangdijia in #2
• Optimize by @huangdijia in #4
• Fix the bug that not run keepalive by @huangdijia in #6
• Fix the bug that set offline do not remove from set by @huangdijia in #8
• Optimize auto cleanup expired clients by @huangdijia in #9

Full Changelog: https://github.com/friendsofhyperf/websocket-cluster-addon/commits/v4.0.0-beta.8