Add Applicative and Monad instances for CofreeT about free HOT 3 CLOSED

instance (Alternative f, Monad w) => Monad (CofreeT f w) where
  return = CofreeT . return . (:< empty)
  {-# INLINE return #-}
  (CofreeT cx) >>= f = CofreeT $ do
    (a :< m) <- cx
    (b :< n) <- runCofreeT $ f a
    return $ b :< (n <|> fmap (>>= f) m)

instance (Alternative f, Applicative w) => Applicative (CofreeT f w) where
  pure = CofreeT . pure . (:< empty)
  {-# INLINE pure #-}
  (CofreeT wf) <*> aa@(CofreeT wa) = CofreeT $
    ( \(f :< t) ->
      \(a) ->
      let (b :< n) = bimap f (fmap f) a in
      b :< (n <|> fmap (<*> aa) t)) <$> wf <*> wa