FORT WORTH, Texas — American Airlines and JetBlue Airways are further increasing competition for travelers in the Northeast. The airlines announced they are adding a variety of new nonstop destinations from New York’s LaGuardia Airport (LGA), Newark Liberty International Airport (EWR) and Boston Logan International Airport (BOS) in 2023. The new service — which includes many routes currently only flown by one other carrier — is made possible through JetBlue and…