docs: move community to Discord

.github/ISSUE_TEMPLATE/config.yml

@@ -3,9 +3,9 @@ contact_links:
   - name: GitHub Discussions
     url: https://github.com/mermaid-js/mermaid/discussions
     about: Ask the Community questions or share your own graphs in our discussions.
-  - name: Slack
-    url: https://join.slack.com/t/mermaid-talk/shared_invite/enQtNzc4NDIyNzk4OTAyLWVhYjQxOTI2OTg4YmE1ZmJkY2Y4MTU3ODliYmIwOTY3NDJlYjA0YjIyZTdkMDMyZTUwOGI0NjEzYmEwODcwOTE
-    about: Join our Community on Slack for Help and a casual chat.
+  - name: Discord
+    url: https://discord.gg/wwtabKgp8y
+    about: Join our Community on Discord for Help and a casual chat.
   - name: Documentation
     url: https://mermaid.js.org
     about: Read our documentation for all that Mermaid.js can offer.

.github/lychee.toml

@@ -34,8 +34,8 @@ exclude = [
 # Don't check files that are generated during the build via `pnpm docs:code`
 'packages/mermaid/src/docs/config/setup/*',
 
-# Ignore slack invite
-"https://join.slack.com/"
+# Ignore Discord invite
+"https://discord.gg"
 ]
 
 # Exclude all private IPs from checking.