message: add URL of the docker container repository
diff: @@ -7,3 +7,5 @@ As root user:
  2. ``docker run -d --name pcm --privileged -p 9738:9738 opcm/pcm``
  This will start pcm-sensor-server container exposing CPU metrics from the whole system at port 9738
  +
  +The URL of the docker container repository: https://hub.docker.com/r/opcm/pcm
  