Add link to 2015.08-rc2 announcement e-mail

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

docs/website/news.html

@@ -13,7 +13,9 @@
     <p>We have a new release candidate! Lots of changes all over the
     tree, see
     the <a href="http://git.buildroot.net/buildroot/plain/CHANGES?id=2015.08-rc2">CHANGES</a>
-    file for details.</p>
+    file for details, and
+    the <a href="http://lists.busybox.net/pipermail/buildroot/2015-August/137879.html">release
+    announcement</a>.</p>
 
     <p>Head to the <a href="/downloads/">downloads page</a> to pick up the
     <a href="/downloads/buildroot-2015.08-rc2.tar.bz2">2015.08-rc2