Resolve against package.json main field

[arei]

I would like includepaths to resolve into a non-standard node_modules location for external entries. This sort of works, if the node_modules path is listed in the paths option. However, it only works for packages that have an index.js as their entry point. Many packages use different entry points as described in the main field of their package.json file. This request is then to resolve packages against their main field if a package.json exists.

A note as well that the package.json main field should resolve before just appending a index.js to the file name.