registry: list mistral project

Change-Id: Icbc73b3df9cedf9bd228c23b20aebf9b69c4a39c
diff --git a/doc/source/plugin-registry.rst b/doc/source/plugin-registry.rst
index 9bc7ce3..1b54c01 100644
--- a/doc/source/plugin-registry.rst
+++ b/doc/source/plugin-registry.rst
@@ -26,6 +26,8 @@
 +--------------------+-------------------------------------------+--------------------+
 |magnum              |git://git.openstack.org/openstack/magnum   |                    |
 +--------------------+-------------------------------------------+--------------------+
+|mistral             |git://git.openstack.org/openstack/mistral  |                    |
++--------------------+-------------------------------------------+--------------------+
 |rally               |git://git.openstack.org/openstack/rally    |                    |
 +--------------------+-------------------------------------------+--------------------+
 |sahara              |git://git.openstack.org/openstack/sahara   |                    |