RFC: Support exports field of package.json

[fastner]

With support of ES modules in Node.js there is a new field exports that defines entry points for different engines (e.g. browser or node) and package formats (e.g. commonjs or ES modules):

https://nodejs.org/api/esm.html#esm_package_entry_points

Make them work in parallel to module, unpkg and types.

[swernerx]

Could be a nice add-on indeed. I see these fields more and more in real life.