Kane Brown says he’s adding a major extension to his Nashville-area home. It’s not quite fair to call it a man cave, as most man caves can’t support a basketball game with an audience. “It’s gonna be sick,” Brown tells Taste of Country Nights host Evan Paul after revealing his plans. The conversation grew out of a question about what he was going to do with all the signed NBA jerseys he’s gotten in recent months and years. Jimmy Butler (Miami Heat) signed a jersey and a pair of game-worn Olympic sneakers for him. Stephen Curry (Golden State Warriors) signed a jersey. Khris Middleton of the cha…