Make sure we notify preact in disconnectedCallback

[freeman]

So that componentWillUnmount lifecycle methods are properly called on any child preact components.

See skatejs/skatejs#1244

[treshugart]

I wonder if it would be better to "unmount" the component, maybe replacing it with a div or something if you can't do that, so that it is compatible with whatever Preact does in the future on unmounting.

[treshugart]

This should also be done in https://github.com/skatejs/renderer-react.

[Hotell]

so this is a bug on our side or on the renderers side @treshugart ?

[treshugart]

@Hotell it should be done within the renderers.