Require interface files

[ghost]

DONE:

• Add a check during the build to ensure that an interface file exists for each module

[vercel]

This pull request is being automatically deployed with Vercel (learn more).
To see the status of your deployment, click below or on the icon next to each commit.

🔍 Inspect: https://vercel.com/ocaml/v3-ocaml-org/CCmFCcizegQVPGa4XFcMvnRxoi3i
✅ Preview: https://v3-ocaml-org-git-kw1-minor-fixes-ocaml.vercel.app

[rdavison]

Looks good to me. Just need to pull in master and delete the InternalUris.resi file.