Update JavaScript codebase to use ESM module

Bug: https://phabricator.wikimedia.org/T407180
Change-Id: I365025bf144f04fe9e9b43d75fffc22fcc0c8625

Author: Abijeet

docs/index.rst

@@ -78,10 +78,10 @@ The basic usage is like this:
 
 .. code-block:: js
 
-		const languageData = require('@wikimedia/language-data');
+		import { getAutonym } from '@wikimedia/language-data';
 
 		// Returns English
-		languageData.getAutonym( 'en');
+		getAutonym( 'en');
 
 The exposed methods are similar to the methods present in the PHP `LanguageUtil <api/languagedata/languageutil.html>`_ class.
 

package.json

@@ -34,7 +34,7 @@
     "url": "http://github.com/wikimedia/language-data/issues"
   },
   "engine": {
-    "node": ">=16.0.0"
+    "node": ">=18.0.0"
   },
   "license": "GPL-2.0-or-later",
   "scripts": {

src/index.js

@@ -1,4 +1,4 @@
-const languageData = require( '../data/language-data.json' );
+import languageData from '../data/language-data.json' assert { type: 'json' };
 
 /**
  * Utility functions for querying language data.
@@ -301,7 +301,7 @@ function addLanguage( code, options ) {
 	}
 }
 
-module.exports = {
+export {
 	addLanguage,
 	getAutonym,
 	getAutonyms,

tests/js/index.js

@@ -1,5 +1,5 @@
-const languageData = require( '../../src/index.js' ),
-	assert = require( 'assert' );
+import * as languageData from '../../src/index.js';
+import assert from 'assert';
 
 describe( 'languagedata', () => {
 	/*