Hydrate App: Incorrect/Missing renderToString Options

[guidoknoll]

The renderToString Options in the Guides/Hydrate App Chapter are incorrect and not well documented.

The afterHydrate and beforeHydrate Options with type boolean already seemed a bit off to me so i analyzed the hydrate build. These are functions with the mocked document as a parameter, so that you can modify the mocked window object before rendering for example.

The other options seem correct and self-explanatory to me.

I'll try opening a PR the next days!