Removed directories field

[ijlee2]

Background

The directories field in a package.json is unnecessary for ESM packages.

The CommonJS Packages spec details a few ways that you can indicate the structure of your package using a directories object. If you look at npm's package.json, you'll see that it has directories for doc, lib, and man.

In the future, this information may be used in other creative ways.

https://docs.npmjs.com/cli/v8/configuring-npm/package-json#directories