Make timeout of wait() customizable

[Junkern]

I have been playing around with chromeless and I noticed, that there is a timeout for the wait() function (https://github.com/graphcool/chromeless/blob/master/src/api.ts#L21).

Would be great to be able to customize that. Not sure if it's better via an options object directly passed to the wait() function or via a global config object passed to the new Chromeless().

I can also make a PR for the chosen option.

[schickling]

This is actually already possible, just seems like we haven't documented it yet (see #54).

You can see here how it works

[Junkern]

Yeah, I noticed that aswell 2 minutes after creating the issue^^