Mariners giving 20-year-old prospect record-breaking $95 million contract

Seattle is taking a big-league swing on its top prospect — before he takes one of his own.  The Mariners have signed wunderkind shortstop Colt Emerson to a historic eight-year, $95 million contract before even making his MLB debut, The Post’s Jon Heyman confirmed Tuesday morning. The deal, pending a physical, would become the largest…