Food stylist Christine Tobin knows how a meal is supposed to look. It’s her job, after all. But thanks to Instagram chefs and cooking shows, now Tobin’s viewers do, too. On “Julia,” HBO Max’s dramedy about iconic chef Julia Child (Sarah Lancashire) that premiered March 31, food isn’t just a prop. It’s the very essence of the show. “You eat with your eyes before your stomach,” Tobin, who has previously worked on projects including “Little Women,” “American Hustle” and “Olive Kitteridge,” told the Daily News. “Julia” begins in 1961 as Child launches “Mastering the Art of French Cooking” into the…