docs/website/news.html: add 2015.05 announcement link

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

docs/website/news.html

@@ -14,7 +14,8 @@
     <p>The stable 2015.05 release is out - Thanks to everyone
     contributing and testing the release candidates. See the
     <a href="http://git.buildroot.net/buildroot/plain/CHANGES?id=2015.05">CHANGES</a>
-    file for more details,
+    file for more details, read the
+    <a href="http://lists.busybox.net/pipermail/buildroot/2015-May/129209.html">announcement</a>
     and go to the <a href="/downloads/">downloads page</a> to pick up the
     <a href="/downloads/buildroot-2015.05.tar.bz2">2015.05 release</a>.</p>