WiredComponent.getInitialProps -> Always async

[gio-work]

Hey there,

We noticed that WiredComponent.getInitialProps is sync on client and async on server. We would be interested in them being async on either or, since it's technically allowed in Next.JS

If this works for y'all, I'm happy to put out a PR.

Thanks!

[rrdelaney]

Don't see any reason that it had to be synchronous, would happily accept a PR! Let's make sure that it's backwards compatible and we can return either the value itself or a promise.