Can't use different ReactRender types in render

[natefaubion]

The polymorphism over render with ReactRender lets you use different return types, but it's fixed for the class, which means you can't return different types on different ticks of render. I should be able to return a String in one render tick, and a ReactElement in another tick. The correct type I think would be:

{ ... render :: forall r. ReactRender r. ReactThis props state => Eff ... r }

Edit: This is actually wrong, since it means render can't fix the type.
But this higher-ranked type is problematic. I think instead we should just define coercions to ReactElement, since these can actually be used anywhere and not just the root of a render.

fromString :: String -> ReactElement
fromInt :: Int -> ReactElement
fromNumber :: Number -> ReactElement
fromArray :: Array ReactElement -> ReactElement

[natefaubion]

I think if we wanted to keep ReactRender, it would be better to actually give it a member, so that it can be overloaded for arbitrary PureScript types.

class ReactRender a where
  toElement :: a -> ReactElement

instance reactRenderString :: ReactRender String where
  toElement = unsafeCoerce :: String -> ReactElement
...

Where the "native" element types are implemented via unsafeCoerce. We should still fix the type of render to return a ReactElement. Users should then opt in with toElement.