Don't work with exports as string

[piranna]

When exports field is an string instead of an object, this module doesn't work. Just by replacing by hand exports for main it works and I can import the package, so probably it's an easy fix at

jest-node-exports-resolver/index.js

Lines 82 to 87 in 276a492

	const hasExports = packageJson && packageJson.exports;
	const isEntryPointsExports =
	hasExports &&
	Object.keys(packageJson.exports).every((k) => k.startsWith("."));
	if (hasExports && isEntryPointsExports) {

[piranna]

Fixed in #6, clossing.