Code review comment for ~jslarraz/review-tools:schema-split-definitions

That's certainly possible as done in https://git.launchpad.net/~jslarraz/review-tools/commit/?id=22827dce8143d4e685f992c049a2935a744285ba.

However, it brings no re usability benefit. For example, looking at this MR https://code.launchpad.net/~jslarraz/review-tools/+git/review-tools/+merge/466454, ideally at some point we would like to validate that the declaration is properly formatted using a declaration schema rather than in code. In such a situation, I think it will be better (for the maintainability) to define the snap types in a separate file that can be imported by both snap.json and declaration.json rather than two separate list.