Merge pull request #38 from unasuke/update-invite-link-20230819

Update slack invitation link

Author: unasuke

_config.yml

@@ -20,4 +20,4 @@ twitter:
   card: summary_large_image
   username: ruby-jp
 
-slack_invite_link: https://join.slack.com/t/ruby-jp/shared_invite/zt-1x6ih6re9-rb_RdylYdnqrVplw278n4Q
+slack_invite_link: https://join.slack.com/t/ruby-jp/shared_invite/zt-21eork7cn-GK5P~~OlmyzC2r~Lpg5ryg