docs,CI: Switch to Libera.Chat

.github/workflows/test.yml

@@ -68,6 +68,7 @@ jobs:
         name: Notify IRC
         uses: Gottox/irc-message-action@v1
         with:
+          server: irc.libera.chat
           channel: '#zsh-syntax-highlighting'
           nickname: zsyh-gh-bot
           message: '${{ github.ref }} failed tests: https://github.com/${{ github.repository }}/actions/runs/${{ github.run_id }}'

HACKING.md

@@ -95,5 +95,5 @@ zstyle ':completion:*:*:*:*:globbed-files' ignored-patterns {'*/',}zsh-syntax-hi
 IRC channel
 -----------
 
-We're on #zsh-syntax-highlighting on freenode.
+We're on #zsh-syntax-highlighting on Libera.Chat.