Add a 6.5.1 landing page.

R1/source/releases/rel6.5.1.rst

+.. _rel6.5.1:
+
+Varnish Cache 6.5.1
+===================
+
+* Source download :download:`varnish-6.5.1.tgz <varnish-6.5.1.tgz>`
+
+* SHA256=11964c688f9852237c99c1e327d54dc487549ddb5f0f5aa7996e521333d7cdb5
+
+Varnish Cache 6.5.1 is a regular bi-annual "fresh" release. It supersedes
+the :ref:`rel6.5.0` release, which is not recommended due to the wrong
+VRT_MAJOR_VERSION version field in the released sources.
+
+More information:
+
+* `changes.rst entry for 6.5.1 <https://github.com/varnishcache/varnish-cache/blob/6.5/doc/changes.rst>`_
+
+For installation instructions including information about cloud images see
+`the Varnish Installation Manual </docs/trunk/installation/index.html>`_
+
+We recommend using the manual installation procedure available at:
+https://packagecloud.io/varnishcache/varnish65/install#manual
+