chore: add redirect

Author: koshachy

redirects/site.yml

@@ -34,6 +34,9 @@
    - /community/kotlin-nights/branding.html
   to: /docs/kotlin-night-guidelines.html
 
+- from: /community/slackccugl.html
+  to: /docs/slack-code-of-conduct.html
+
 - from: /docs/reference/compatibility.html
   to: /docs/reference/evolution/components-stability.html
 
@@ -55,4 +58,4 @@
   to: https://kotlinfoundation.org/submitting-incompatible-changes/
 
 - from: /docs/foundation-faq.html
-  to: https://kotlinfoundation.org/faq/
+  to: https://kotlinfoundation.org/faq/