Live Media welcome text should give user hints how to use the command line

[kobliha]

After logging into the console or via ssh, the user simply gets "Have a lot of fun" message. Thanks a lot for that ;) but I'd love to get some hints about what I should do here. Especially some hints about the agama command and how to get the help/more info or where to find the docs, e.g. link to the https://agama-project.github.io/ page.