Document SSR with v3

[lorensr]

v2 SSR docs: https://www.apollographql.com/docs/react/recipes/meteor.html#SSR

This looks like it should work, but I haven't tested it:

https://github.com/apollographql/meteor-integration/issues/122

Would be good to implement it in https://github.com/lorensr/test-meteor-apollo/