Add modern ESM Support

[nrcrast]

Fix #59

This updates the tsconfig and package.json (and all the other consequences of that) to export proper ESM modules.

You can test this pretty easily with a project like the following:

package.json

{
  "name": "json-validator-test",
  "version": "1.0.0",
  "type": "module",
  "scripts": {
    "start": "node src/index.js",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "description": "",
  "dependencies": {
    "json-schema-library": "10.5.2",
    "tsx": "^4.19.3"
  },
  "devDependencies": {
    "@types/node": "^24.0.3",
    "typescript": "^5.8.3"
  }
}

src/index.js

import {compileSchema} from "json-schema-library";

const schema = compileSchema({
  "$id": "https://example.com/person.schema.json",
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "title": "Person",
  "type": "object",
  "properties": {
    "firstName": {
      "type": "string",
      "description": "The person's first name."
    }
  }
});

console.log('Hello world', schema);

Using plain ole npm with node v22, running npm i && npm run start you'll get something like this:

file:///Users/206674672/code/json-validator-test/src/index.js:1
import {compileSchema} from "json-schema-library";
        ^^^^^^^^^^^^^
SyntaxError: Named export 'compileSchema' not found. The requested module 'json-schema-library' is a CommonJS module, which may not support all module.exports as named exports.
CommonJS modules can always be imported via the default export, for example using:

import pkg from 'json-schema-library';
const {compileSchema} = pkg;

    at ModuleJob._instantiate (node:internal/modules/esm/module_job:177:21)
    at async ModuleJob.run (node:internal/modules/esm/module_job:260:5)
    at async onImport.tracePromise.__proto__ (node:internal/modules/esm/loader:543:26)
    at async asyncRunEntryPointWithESMLoader (node:internal/modules/run_main:116:5)

Replacing the version with my branch: :

    "json-schema-library": "git@github.com:nrcrast/json-schema-library.git#66bb39f1b68d518ee67707d88ea0598dec7e8a51",

You'll get the expected output where it dumps the whole compiled schema:

> json-validator-test@1.0.0 start
> node src/index.js

Hello world <ref *1> {
  evaluationPath: '#',
  lastIdPointer: '#',
  schemaLocation: '#',
  dynamicId: '',
....etc

[sagold]

Hi Nick,

thank you for your PR!! I will need some time to verify your changes and test other types of exports. I have a setup
prepared to build an esm module without those changes, but your PR might be a better way forward.

Cheers,
Sascha