Update slack invite link

Relequestual · Relequestual · commit d7c7f15d7d71 · 2023-04-17T12:32:31.000+01:00
Previous one expired, so new slack invite link!
The link doesn't have an expiery date, but sometimes expires after some number of uses... number unknown or not documented by Slack as far as I can tell.
diff --git a/slack.md b/slack.md
@@ -1,3 +1,3 @@
 ---
-redirect_to: https://join.slack.com/t/json-schema/shared_invite/zt-15ylccbuu-3T2bRia8uzhE157TSW6nXg
+redirect_to: https://join.slack.com/t/json-schema/shared_invite/zt-1tc77c02b-z~UiKXqpM2gHchClKbUoXw
 ---

-Original file line number
+Diff line change
@@ @@ -1,3 +1,3 @@ @@
 ---
 -redirect_to: https://join.slack.com/t/json-schema/shared_invite/zt-15ylccbuu-3T2bRia8uzhE157TSW6nXg
 +redirect_to: https://join.slack.com/t/json-schema/shared_invite/zt-1tc77c02b-z~UiKXqpM2gHchClKbUoXw
 ---