exposed createBatchingNetworkInterface from apollo-client

[shian15810]

Exposed createBatchingNetworkInterface from apollo-client so that it can be imported from react-apollo just like createNetworkInterface.

TODO:

• If this PR is a new feature, reference an issue where a consensus about the design was reached (not necessary for small changes)
• Make sure all of the significant new logic is covered by tests
• Rebase your changes on master so that they can be merged easily
• Make sure all tests and linter rules pass
• Update CHANGELOG.md with your change
• If this was a change that affects the external API, update the docs and post a link to the PR in the discussion

[apollo-cla]

@shian15810: Thank you for submitting a pull request! Before we can merge it, you'll need to sign the Meteor Contributor Agreement here: https://contribute.meteor.com/

[helfer]

Thanks @shian15810 ! 🙂