[discuss] Adopt style splitting

[jsanz]

The OpenMapTiles main repo has adopted style splitting across layer definitions with a new tool added to the tools repo. This makes maintaining the styles much simpler and easier to review and reuse.

Would it makes sense for the bright style to adopt the same approach? We (Elastic) have just started using it in our own modified version of this style (you can take a look at this PR) and even we are still keeping the, now generated, style.json file, we can track changes on each layer separately.

We are happy to create a similar PR here if this is useful for others.

What do you think?