NEW PITCH: Washington Nationals pitcher Gio Gonzalez found a way to stay busy in the off-season: become a fashion designer. The lefty hurler on Monday will begin selling a collection of men’s, women’s and children’s T-shirts on a new e-commerce site, Thehouseofleagues.com. The Ts, which will retail for $24 to $68, feature graphic representations of old-fashioned stickball and include a stick figure insignia and traditional baseball references such as hot dogs and beer. The 100 percent cotton styles include crewnecks and V-necks for men, crop tops, raglans, sweatshirts and tanks for women, and raglans and Ts for kids. Later this year, Gonzalez will broaden the offering into woven tops and jeans, the price points of which haven’t been determined.