Implement #hash import resolution for package.json imports

[larsmoa]

Summary

Adds support for resolving #hash imports defined in the imports field of package.json.

Motivation

This change will enable e.g. madge to properly resolve #hash-style imports. See pahen/madge#406.

Currently, imports like:

import { openAggregate } from "#aggregate";
import { Button } from "#lib/button";

...fail to resolve when the package.json contains:

{
  "imports": {
    "#aggregate": "./src/util/aggregate.js",
    "#lib/*": "./src/lib/*.js"
  }
}

This causes madge to skip these dependencies entirely, making dependency graphs incomplete for projects using Node.js subpath imports.

Solution

This PR adds hash import resolution by leveraging enhanced-resolve (already a dependency) which fully supports the Node.js subpath imports specification including:

• Exact matches (#utils → ./src/utils.js)
• Wildcard patterns (#lib/* → ./src/lib/*.js)
• Conditional imports (import, require, node, default conditions)
• Nested conditions

References

• Upstream Issue: Support package.json "imports" field ("#hash"-style imports) pahen/madge#406
• Node.js Subpath Imports Spec: https://nodejs.org/api/packages.html#subpath-imports

[XhmikosR]

I could use more eyes on this PR...

[markmssd]

Hoping to see this PR land soon, so we can leverage it in Madge! Btw, in our case, the imports config looks like this:

  "imports": {
    "#utils/*": {
      "types": [
        "./*.tsx",
        "./*.ts",
        "./*.js",
        "./*/index.ts"
      ],
      "default": "./*"
    }
  },

@larsmoa would it be supported?