Publish a "realm-schema-exporter" package

[kraenhansen]

As a user of Realm, I would like to automate generating the language specific code representing the schema across multiple platforms / languages. Ideally this would be a package published on NPM with a simple CLI as well as exports.

Currently Realm Studio has a feature to export the schema of a local or synchronized Realm into multiple languages, but it requires manual interaction with Realm Studio (opening the Realm, selecting stuff from the menu).

The part of Realm Studio responsible for this is highly decoupled from the rest of Realm Studio: https://github.com/realm/realm-studio/tree/master/src/services/schema-export and it should be fairly easy to refactor and publish this as a separate package on NPM.

I'm creating the issue in this repository, be cause I think this repo (or perhaps https://github.com/realm/realm-tools) would be a good place to move the current code.