[libcxx-commits] [libcxx] [libc++][doc] Update the release notes for LLVM 18 (PR #78324)

[Christopher Di Bella via libcxx-commits]

================
@@ -35,9 +35,25 @@ see the `releases page <https://llvm.org/releases/>`_.
 What's New in Libc++ 18.0.0?
 ==============================
 
-- A new debug mode has been added, replacing the legacy debug mode that was
-  removed in the LLVM 17 release. See ``libcxx/docs/Hardening.rst`` for more
-  details.
+The main focus of the libc++ team has been to implement new C++20, C++23,
+and C++26 features.
+
+A new debug mode has been added, replacing the legacy debug mode that was
+removed in the LLVM 17 release. See :ref:`hardening-modes` for more details.
----------------
cjdb wrote:

```suggestion
A new debug mode replaced the legacy debug mode. See :ref:`hardening-modes` for more details.
```

https://github.com/llvm/llvm-project/pull/78324