feat(doc): update slack channel

Signed-off-by: ngjaying <ngjaying@gmail.com>

README-CN.md

@@ -65,7 +65,7 @@ Kuiper 可以运行在各类物联网的边缘使用场景中，比如工业物
 - [Forum](https://askemq.com/c/kuiper/)
 - [Weibo](https://weibo.com/emqtt)
 - [Blog](https://www.emqx.cn/blog)
-- [Slack](https://kuiper-slack-invite.emqx.io/)
+- [Slack](https://join.slack.com/t/lfedge/shared_invite/zt-7kavdtmq-SeyFzM2CEABBcKYGEVCgkw): 加入 [ekuiper](https://lfedge.slack.com/archives/C024F4P7KCK) 或者 [ekuiper-user](https://lfedge.slack.com/archives/C024F4SMEMR) 频道。
 - [Twitter](https://twitter.com/EMQTech)
 - [Reddit](https://www.reddit.com/r/emqx/)
 - [Facebook](https://www.facebook.com/emqxmqtt)

README.md

@@ -62,7 +62,7 @@ It can be run at various IoT edge use scenarios, such as real-time processing of
 - [EdgeX rule engine tutorial](docs/en_US/edgex/edgex_rule_engine_tutorial.md)
 
 ## Slack channels
-Join our [Slack](https://kuiper-slack-invite.emqx.io/).
+Join our [Slack](https://join.slack.com/t/lfedge/shared_invite/zt-7kavdtmq-SeyFzM2CEABBcKYGEVCgkw), and then join [ekuiper](https://lfedge.slack.com/archives/C024F4P7KCK) or [ekuiper-user](https://lfedge.slack.com/archives/C024F4SMEMR) channel.
 
 ## Performance test result
 

docs/en_US/README.md

@@ -53,7 +53,7 @@ It can be run at various IoT edge use scenarios, such as real-time processing of
 - [EdgeX rule engine tutorial](./edgex/edgex_rule_engine_tutorial.md)
 
 ## Slack channels
-Join our [Slack](https://join.slack.com/t/emqx/shared_invite/zt-7xrracuf-GGdbNB1pARtaZKvv6IfTvw), and then join [kuiper](https://emqx.slack.com/archives/C0138SZP23Y) channel.
+Join our [Slack](https://join.slack.com/t/lfedge/shared_invite/zt-7kavdtmq-SeyFzM2CEABBcKYGEVCgkw), and then join [ekuiper](https://lfedge.slack.com/archives/C024F4P7KCK) or [ekuiper-user](https://lfedge.slack.com/archives/C024F4SMEMR) channel.
 
 ## Performance test result
 

docs/zh_CN/README.md

@@ -53,7 +53,7 @@ Kuiper 可以运行在各类物联网的边缘使用场景中，比如工业物
 - [EdgeX 规则引擎教程](./edgex/edgex_rule_engine_tutorial.md)
 
 ## Slack
-加入我们的 [Slack](https://join.slack.com/t/emqx/shared_invite/zt-7xrracuf-GGdbNB1pARtaZKvv6IfTvw)，然后加入 [kuiper](https://emqx.slack.com/archives/C0138SZP23Y) 频道。
+加入我们的 [Slack](https://join.slack.com/t/lfedge/shared_invite/zt-7kavdtmq-SeyFzM2CEABBcKYGEVCgkw)，然后加入 [ekuiper](https://lfedge.slack.com/archives/C024F4P7KCK) 或者 [ekuiper-user](https://lfedge.slack.com/archives/C024F4SMEMR) 频道。
 
 ## 性能测试结果