This PR adds a script that generates a new Reason module named `Fnm__Package` and a script that verifies that it is up to date.
`Fnm__Package` will have `package.json` information necessary for the app, like its version.
Unfortunately, [`husky` doesn't work with esy](https://github.com/esy/esy/issues/623) so I can't use it for generating git hooks and have a `pre-commit` script that verifies `Fnm__Package` and reformats using `refmt`
Corentin Leruth