Merge pull request moby#29468 from hongbin/volume-plugin-fuxi

Add Fuxi Volume Plugin to the docs
(cherry picked from commit 13f4576)

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
(cherry picked from commit a2ca630)
Signed-off-by: Tibor Vass <tibor@docker.com>

docs/extend/legacy_plugins.md

@@ -65,6 +65,7 @@ Plugin
 [Convoy plugin](https://github.com/rancher/convoy)                                  | A volume plugin for a variety of storage back-ends including device mapper and NFS. It's a simple standalone executable written in Go and provides the framework to support vendor-specific extensions such as snapshots, backups and restore.
 [DRBD plugin](https://www.drbd.org/en/supported-projects/docker)                    | A volume plugin that provides highly available storage replicated by [DRBD](https://www.drbd.org). Data written to the docker volume is replicated in a cluster of DRBD nodes.
 [Flocker plugin](https://clusterhq.com/docker-plugin/)                              | A volume plugin that provides multi-host portable volumes for Docker, enabling you to run databases and other stateful containers and move them around across a cluster of machines.
+[Fuxi Volume Plugin](https://github.com/openstack/fuxi)                             | A volume plugin that is developed as part of the OpenStack Kuryr project and implements the Docker volume plugin API by utilizing Cinder, the OpenStack block storage service.
 [gce-docker plugin](https://github.com/mcuadros/gce-docker)                         | A volume plugin able to attach, format and mount Google Compute [persistent-disks](https://cloud.google.com/compute/docs/disks/persistent-disks).
 [GlusterFS plugin](https://github.com/calavera/docker-volume-glusterfs)             | A volume plugin that provides multi-host volumes management for Docker using GlusterFS.
 [Horcrux Volume Plugin](https://github.com/muthu-r/horcrux)                         | A volume plugin that allows on-demand, version controlled access to your data. Horcrux is an open-source plugin, written in Go, and supports SCP, [Minio](https://www.minio.io) and Amazon S3.