Respect the user's actual map keybinding instead of hardcoding M (#33)
Bindings.lua always stole the literal "M" key, ignoring any custom
binding the user had set for the default map. Now it reads
GetBindingKey("TOGGLEWORLDMAP") to find the real key to take over,
and skips rebinding entirely once GOGGLEMAPS_TOGGLEMAP already has
a saved binding so it doesn't fight manual rebinds.