Docs: Add subscription network config example (#3062)
Docs: Add subscription network config example (#3062)

Summary:
Resolves https://github.com/facebook/relay/issues/2949

Related issue and comment: https://github.com/facebook/relay/issues/2869#issuecomment-534905537

Pull Request resolved: https://github.com/facebook/relay/pull/3062

Reviewed By: tyao1

Differential Revision: D22484370

Pulled By: dadapoof

fbshipit-source-id: 9a3e9626787e2fa0f1d6e7c6a8e63844052b7f99

kassens/relay,kassens/relay,wincent/relay,voideanvalue/relay,facebook/relay,xuorig/relay,xuorig/relay,atxwebs/relay,atxwebs/relay,yungsters/relay,xuorig/relay,josephsavona/relay,yungsters/relay,facebook/relay,xuorig/relay,atxwebs/relay,kassens/relay,facebook/relay,xuorig/relay,facebook/relay,wincent/relay,wincent/relay,josephsavona/relay,kassens/relay,yungsters/relay,voideanvalue/relay,kassens/relay,josephsavona/relay,atxwebs/relay,kassens/relay,voideanvalue/relay,voideanvalue/relay,voideanvalue/relay,wincent/relay,facebook/relay,wincent/relay,facebook/relay,wincent/relay,xuorig/relay,voideanvalue/relay