Add main file for babel-node

[dword-design]

Q	A
Fixed Issues?
Patch: Bug Fix?	Yes
Major: Breaking Change?
Minor: New Feature?
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?
License	MIT

It sometimes makes sense to require.resolve a package in order to look for certain information/files. E.g. https://www.npmjs.com/package/depcheck parses the binaries from packages in order to find out if it's an unused dependency. However, this requires the packages to have a main file. This PR simply adds lib/babel-node.js as the main fine.

[JLHwung]

I'm conservative on this change as adding a main entry will enable people to use require("@babel/node"), which we are not meant for.

Could Special options help depcheck to detech @babel/node?

[dword-design]

Hey @JLHwung, bin special is in fact the special I'm using. This uses resolveFrom, which in turn uses require.resolve. Other options like resolve-bin also use require.resolve, so it always seems to come down to that :P.