Add release note README file

Has instructions on how to run reno, and a link to the
openstack.org docs.  Copied from neutron.

Change-Id: Id38f6bb963cb04c7ba9ae0a0c10fac7b69b2613d

releasenotes/source/README.rst

@@ -0,0 +1,34 @@
+========================================
+OVN Octavia Provider Release Notes Howto
+========================================
+
+Release notes are a new feature for documenting new features in
+OpenStack projects. Background on the process, tooling, and
+methodology is documented in a `mailing list post by Doug Hellmann <http://lists.openstack.org/pipermail/openstack-dev/2015-November/078301.html>`_.
+
+Writing release notes
+---------------------
+
+For information on how to create release notes, please consult the
+`reno documentation <https://docs.openstack.org/reno/latest/user/usage.html>`__.
+
+Please keep the following in your mind when you write release notes.
+
+* **Avoid using "prelude" section** for individual release notes.
+  "prelude" section is for general comments about the release.
+* **Use one entry per section** (like "feature" or "upgrade").
+  All entries which belong to a same release will be merged and rendered,
+  so there is less meaning to use multiple entries by a single topic.
+
+Maintaining release notes
+-------------------------
+
+.. warning::
+
+   Avoid modifying an existing release note file even though it is related
+   to your change. If you modify a release note file of a past release,
+   the whole content will be shown in a latest release. The only allowed
+   case is to update a release note in a same release.
+
+   If you need to update a release note of a past release,
+   edit a corresponding release note file in a stable branch directly.

releasenotes/source/index.rst

@@ -7,3 +7,8 @@
 
    unreleased
    ussuri
+
+.. toctree::
+   :maxdepth: 1
+
+   README.rst