[clang] [clang][www] Replace mailing list reference with Discourse forum link (PR #228676)

[Ivy Xu via cfe-commits]

https://github.com/IvyXu420 created https://github.com/llvm/llvm-project/pull/228676

LLVM is now migrating from the mailing lists to Discourse (https://llvm.org/docs/DiscourseMigrationGuide.html),
but https://clang.llvm.org still suggests signing up for a mailing list. This PR replaces that recommendation with the Clang Frontend Discourse forum.

>From 6a0223694dc1acf357fcc6403fbef62d35f0f6a9 Mon Sep 17 00:00:00 2001
From: Ivy Xu <fakeshadow1337 at gmail.com>
Date: Sat, 3 Oct 2026 15:48:39 +0800
Subject: [PATCH] Recommend Discourse instead of mailing list on website

---
 clang/www/index.html | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/clang/www/index.html b/clang/www/index.html
index 465a6a6d29dc76..6b50be906aa2cb 100755
--- a/clang/www/index.html
+++ b/clang/www/index.html
@@ -103,8 +103,9 @@ <h2>Get it and get involved!</h2>
      involved in the Clang community</a>.  The Clang developers include numerous
      volunteer contributors with a variety of backgrounds.  If you're
      interested in
-     following the development of Clang, signing up for a mailing list is a good
-     way to learn about how the project works.</p>
+     following the development of Clang, signing up for the
+     <a href="https://discourse.llvm.org/c/clang/6">Clang Frontend Discourse forum</a> 
+     is a good way to learn about how the project works.</p>
 </div>
 </body>
 </html>