[Feature] In-game map marker commands

[McSnurtle]

Describe the feature

Similar to how dynmap used /dmarker in-game, admins could use the /marker command to register markers on the worldmap website without needing to touch configs or restart anything!

What problems does this feature solve / cause?

Solves delving into configs and numerical values instead of a having a visual approach where you can actually see what you're doing.

Which pre-existing system does this feature tie into?

Other

Additional context

https://modrinth.com/plugin/bmarker