Add note about the transition to Moby in the README

Signed-off-by: Tibor Vass <tibor@docker.com>

README.md

@@ -1,3 +1,6 @@
+**Docker is transitioning to the Moby Project. [Click here for more information](https://github.com/moby/moby/pull/32691)**
+---------------
+
 Docker: the container engine [![Release](https://img.shields.io/github/release/docker/docker.svg)](https://github.com/docker/docker/releases/latest)
 ============================