add a few example seeds to the top

[maskersss]

idk how good of an idea it is, but my reasoning is that it doesn't seem to be very obvious to people how to copy a part of a json, and editing an already existing entry should be more intuitive

[tildejustin]

that would be more appropriate for the set-spawn readme I think (https://github.com/Minecraft-Java-Edition-Speedrunning/set-spawn). It needs an update anyway.