A cooperative pop-up gallery at the Malia Mills swimsuit boutique on Main Street in East Hampton has energized the space, previously empty in the off-season, with art exhibitions and readings. Drama will be added to the mix on Saturday at 6:30 p.m. when Chloe Dirksen and J. Stephen Brantley perform a staged reading of “May 39th,” a 40-minute play by Callie Kimball.