doc: update documentation with Libera.chat IRC channel

README

@@ -66,7 +66,7 @@ or live capturing, saving packets to a new file
 You can configure some options using [sngreprc](https://github.com/irontec/sngrep/wiki/Configuration) file
 
 ## Frequent Asked Questions
-Any feedback, request or question are welcomed at [#sngrep](https://webchat.freenode.net/?channels=sngrep) channel at irc.freenode.net
+Any feedback, request or question are welcomed at [#sngrep](https://kiwiirc.com/nextclient/irc.libera.chat/#sngrep) channel at irc.libera.chat
 
 See FAQ on [Github Wiki](https://github.com/irontec/sngrep/wiki#frequent-asked-questions)