Add `ToList` class

As an alternative to https://github.com/purescript/purescript-foldable-traversable/issues/69, we could add a class:

```purescript
class ToList f where
  toList :: forall a. f a -> LL.List a
  foldrLazy :: forall a b. Z.Lazy b => (a -> b -> b) -> b -> f a -> b
```

Where
```
toList f = foldrLazy LL.cons LL.nil f
foldrLazy cons nil f = LL.foldrLazy cons nil (toList f)
```