run backend graphql standalone

Hello,

First of all congrats for this great work!
Is there a way to run the backend standalone i.e. only the graphql endpoint without the react frontend?
I see the `backend` directory could do the job, but it seems its code is somehow duplicated in `react-app/pages/api`, and it would require some minor refactoring for instance to accept Hasura endpoint and admin secret from env vars.

And also ideally: do you plan to build and maintain it in the official Hasura Docker Hub repository?
Thanks in advance!