Suggestions

Thanks for sharing your code, @anmonteiro! 🙏It's great to have some more examples out there.

Two quick suggestions/questions:

- Could some of the usages of `io_field` be replaced with `field` to avoid `Lwt_result.return`, e.g. [this one](https://github.com/anmonteiro/reason-graphql-fullstack/blob/85dd67be8f3f4ea663f0834e5ff280a24cea618b/src/server/schema.re#L41-L47)?
- Could you use use HTTP server that ships with `graphql-lwt`, or does it lack some feature compared to the one you implemented? At a glance they seem quite similar.