merge method
other applied after this one: its entries and curves win, the longer duration is kept.
Implementation
MarkerTransition merge(MarkerTransition other) => MarkerTransition(
duration: other.duration > duration ? other.duration : duration,
appearFrom: {...appearFrom, ...other.appearFrom},
disappearTo: {...disappearTo, ...other.disappearTo},
moveCurve: other.moveCurve,
fadeInCurve: other.fadeInCurve,
fadeOutCurve: other.fadeOutCurve,
);