If a server doesn't have any Terra worlds, warning-level log a message containing a link to the quick start guide.

People don't like to read things, so they don't read the quick start guide, this will make it a tiny bit harder for them to escape reading the instructions.

Do we still want to support this? Because I know we are more or less deprecating support for bukkit/spigot.

We still support Paper. People who use Paper also don't read, so we should do this still.

(No-brainer but worth mentioning): Don't log this on the Forge/Fabric client.

This message should be scheduled to be logged once the server is completely finished starting, so it's the first thing people see in their consoles.
There should also be a config.yml option to disable it.

I'll try and do this in #165