Add a `BindLeft` type class

```purescript
class BindLeft m where
  lbind :: forall a b r. m a r -> (a -> m b r) -> m b r

class (Biapplicative m, BindLeft m) <= MonadLeft m
```

This is a generalized, type-changing `catch` operation, which is useful for things like `Either`, and also lets you implement a `Monad` instance for `Flip`.