title: How to modularize GraphQL schema when using `buildSchema`?
body: <p>It has been about a year since I updated my graphql-js dependency. I see now that there is a utility that simplifies schema generation: <code>buildSchema</code>. This function takes, as an arg, your entire schema, as a string, in the GraphQL language. That's awesome, but is there a way to modularize this? My schema is not super small, and would suck to cram into a single <code>.graphql</code> file. Is there some sort of utility or pattern for storing each type definition in its own file, for example?</p>