get Style Transition
Returns the map style's transition options. By default, the style parser will attemptto read the style default transition options, if any, fallbacking to an immediate transitionotherwise. Transition options can be overriden via `setStyleTransition`, but the options arereset once a new style has been loaded.The style transition is re-evaluated when a new style is loaded.
Return
The `transition options` of the current style in use.