Dynmap Hook

[TheWranger]

Is your feature request related to a problem? Please describe.
Island owners do not have a good way of putting markers on dynmap.

Describe the solution you'd like
Warp signs should show up as markers on dynmap with the sign text attached to it. Server owners should have the ability to customize what icon is used for the marker.

Additional context
Related to BentoBoxWorld/BentoBox#475

[Poslovitch]

This should wait for BentoBox to implement the Hook.

[TheWranger]

Yea, just wanted to post this now so it wouldn't get forgotten about.