v2.1.0-rc3 is not working, please modify the introduction.md

[pandaoknight]

BUG REPORT
The version v2.1.0-rc3 is required in https://github.com/apache/rocketmq-client-go/blob/master/docs/Introduction.md,
Which cause nil pointer panic.

rocketmq-client-go
version: v2.1.0-rc3
os: windows

rocketmq namesrv & broker
os: WSL ubuntu
version: 5.0.0

Document Enhancement
Whereas v2.1.1 works properly, and don't have typo of 'resolver'.
Please modify the introduction.md.

[ShannonDing]

hi, a new PR to update the introduction is welcomed.