Migrate postinstall script to use modules

extensions/package.json

@@ -7,7 +7,7 @@
     "typescript": "4.6.2"
   },
   "scripts": {
-    "postinstall": "node ./postinstall"
+    "postinstall": "node ./postinstall.mjs"
   },
   "devDependencies": {
     "esbuild": "^0.11.12",

extensions/postinstall.mjs

@@ -2,15 +2,12 @@
  *  Copyright (c) Microsoft Corporation. All rights reserved.
  *  Licensed under the MIT License. See License.txt in the project root for license information.
  *--------------------------------------------------------------------------------------------*/
-// @ts-check
 
-'use strict';
+import * as fs from 'fs';
+import path from 'path';
+import { fileURLToPath } from 'url';
 
-const fs = require('fs');
-const path = require('path');
-const rimraf = require('rimraf');
-
-const root = path.join(__dirname, 'node_modules', 'typescript');
+const root = path.join(path.dirname(fileURLToPath(import.meta.url)), 'node_modules', 'typescript');
 
 function processRoot() {
 	const toKeep = new Set([
@@ -21,7 +18,7 @@ function processRoot() {
 		if (!toKeep.has(name)) {
 			const filePath = path.join(root, name);
 			console.log(`Removed ${filePath}`);
-			rimraf.sync(filePath);
+			fs.rmSync(filePath, { recursive: true });
 		}
 	}
 }