Feature: Support ESM subpath _imports_

[ryan-roemer]

Ugh. 🤦

• https://nodejs.org/api/packages.html#packages_imports
• https://nodejs.org/api/packages.html#packages_subpath_imports

// package.json
{
  "imports": {
    "#dep": {
      "node": "dep-node-native",
      "default": "./dep-polyfill.js"
    }
  },
  "dependencies": {
    "dep-node-native": "^1.0.0"
  }
}

and you can then import "#dep" within the module...