Document `enableStaticRendering` about mobx-react

[danielkcz]

@cmdcolin https://github.com/mobxjs/mobx-react#server-side-rendering-with-enablestaticrendering

@mweststrate Looks like it has slipped up from the main docs after all.

[cmdcolin]

Thanks, that definitely makes sense. I'll close for now

[cmdcolin]

ps: I know this is just crazy but we actually do what is done in the codesandbox e.g. ssr on the client side (sometimes in a web worker, sometimes in the main thread, but we may have to stop the main thread ssr'ing)

[mweststrate]

I'd swear I wrote docs on it, but missed something else already as well. I guess I messed up a docs merge somewhere

[mweststrate]

Added to the main docs as well