[wwwdocs] document modula-2 in gcc-13/changes.html (and index.html)

[Gaius Mulley <gaiusmod2@gmail.com>]

Hello,

The following patch provides a summary of the modula-2 front end
and also contains links to the online modula-2 documentation in
index.html.

[I'm just about to git push fixes so that modula-2 builds html, info and
 pdf documentation into the standard directories.]

regards,
Gaius




diff --git a/htdocs/gcc-13/changes.html b/htdocs/gcc-13/changes.html
index 9ecd115c..fa13369f 100644
--- a/htdocs/gcc-13/changes.html
+++ b/htdocs/gcc-13/changes.html
@@ -283,6 +283,18 @@ a work-in-progress.</p>
 
 <!-- <h3 id="go">Go</h3> -->
 
+<h3 id="modula2">Modula-2</h3>
+<ul>
+  <li>Support for the language Modula-2 has been added.  The dialects
+  supported are PIM2, PIM3, PIM4 and ISO/IEC 10514-1.  Also included
+  are a complete set of ISO/IEC 10514-1 libraries and PIM
+    libraries.</li>
+  <li><a href="https://gcc.gnu.org/onlinedocs/m2/Compiler-options.html">
+      Compiler options</a>.</li>
+  <li>The <code><* noreturn *></code> attribute is supported.</li>
+  <li>Linking has been redesigned.</li>
+</ul>
+
 <!-- .................................................................. -->
 <!-- <h2 id="jit">libgccjit</h2> -->
 
diff --git a/htdocs/onlinedocs/index.html b/htdocs/onlinedocs/index.html
index 343ff9f5..27a8a505 100644
--- a/htdocs/onlinedocs/index.html
+++ b/htdocs/onlinedocs/index.html
@@ -1647,6 +1647,12 @@ existing release.</p>
            href="https://gcc.gnu.org/onlinedocs/gdc.ps.gz">PostScript</a> or <a
            href="https://gcc.gnu.org/onlinedocs/gdc-html.tar.gz">an
            HTML tarball</a>)</li>
+    <li><a href="https://gcc.gnu.org/onlinedocs/m2/">GNU M2 Manual</a> (<a
+           href="https://gcc.gnu.org/onlinedocs/m2.pdf">also in
+           PDF</a> or <a
+           href="https://gcc.gnu.org/onlinedocs/m2.ps.gz">PostScript</a> or <a
+           href="https://gcc.gnu.org/onlinedocs/m2-html.tar.gz">an
+           HTML tarball</a>)</li>
     <li><a href="https://gcc.gnu.org/onlinedocs/libgomp/">GNU Offloading and
            Multi Processing Runtime Library Manual</a> (<a
            href="https://gcc.gnu.org/onlinedocs/libgomp.pdf">also in