Recommend to users that features go to the forum first

Co-authored-by: Lily Foote <code@lilyf.org>

Author: tomkins

trac-env/templates/custom_ticket.html

@@ -9,8 +9,12 @@ <h2>Please read this first:</h2>
         Contact <a href="mailto:security@djangoproject.com">security@djangoproject.com</a> instead.</strong>
     </li>
     <li>
-      Report bugs and suggest features in Django itself (or its
-      documentation) using this ticket tracker.
+      Report bugs and suggest documentation changes using this ticket tracker.
+    </li>
+    <li>
+      New feature proposals should first be discussed on the <a href="https://forum.djangoproject.com/c/internals/5">Django Forum</a>.
+      Once feedback has been gathered, you can use this ticket tracker to open a ticket for the new feature.
+      Please include links to relevant discussions from the forum (or other sources).
     </li>
     <li>
       Don't use the ticket system for