Update link to Docker Hub in README

Link was not the public one, this one is

README.md

 the [example config](examples/irccat.json)
 in `/etc/irccat.json` or the local directory and customise it, and run!
 
-A Docker container is also [provided on Docker Hub](https://hub.docker.com/repository/docker/irccloud/irccat).
+A Docker container is also [provided on Docker Hub](https://hub.docker.com/r/irccloud/irccat).
 
 ## TCP → IRC