[wwwdocs] Add C++23 library additions to GCC 13 release notes

[Jonathan Wakely <jwakely@redhat.com>]

Pushed to wwwdocs.

---
 htdocs/gcc-13/changes.html | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/htdocs/gcc-13/changes.html b/htdocs/gcc-13/changes.html
index 390193ca..a7d88038 100644
--- a/htdocs/gcc-13/changes.html
+++ b/htdocs/gcc-13/changes.html
@@ -158,7 +158,22 @@ a work-in-progress.</p>
       warnings have been extended to warn in more contexts.</li>
 </ul>
 
-<!-- <h4 id="libstdcxx">Runtime Library (libstdc++)</h4> -->
+<h4 id="libstdcxx">Runtime Library (libstdc++)</h4>
+<ul>
+  <li>Improved experimental support for C++23, including:
+    <ul>
+    <li>Additions to the <code>&lt;ranges&gt;</code> header:
+      <code>views::zip</code>, <code>views::zip_transform</code>,
+      <code>views::adjacent</code>, <code>views::adjacent_transform</code>
+      <code>views::pairwise</code>, <code>views::slide</code>,
+      <code>views::chunk</code>, <code>views::chunk_by</code>.
+    </li>
+    </ul>
+  </li>
+  <li>Support for the <code>&lt;experimental/scope&gt;</code> header
+      from v3 of the Library Fundamentals Technical Specification.
+  </li>
+</ul>
 
 <!-- <h3 id="d">D</h3> -->
 
-- 
2.37.3