[Feature] auto pause fill on player connect

[4rz0]

This request is for adding an optional auto-pause feature to the worldborder config.
If active, in case a worldborder fill is running, make it pause once a player connects, and resume once the last player disconnects, after an optional cooldown time.
This way, the system can automatically run at the optimal time without disrupting gameplay.

[roopekoo]

@Brettflan I would like to see this option to be in the plugin as well.