Add step to add `apollo.config.js`

Have had a few intercom users saying they ran `npx apollo service:check && npx apollo service:push` and got `Error: No service found to link to Engine`

The tutorial page doesn't currently mention anything about configs

https://www.apollographql.com/docs/tutorial/production.html

There are docs for service settings from the apollo-tooling readme that can be used as reference - https://github.com/apollographql/apollo-tooling#service-settings

Related: https://github.com/apollographql/apollo-tooling/issues/771

Start with the production tutorial page linked in the issue and compare its service settings guidance with the apollo-tooling README reference. Update the tutorial to explain the required apollo.config.js setup before the service:check and service:push commands, then verify that the documented flow addresses the reported error.

Written by the indexing model from the issue text.