Fix lint errors in our npm scripts (microsoft#159501)

Author: mjbvz

build/npm/jsconfig.json

@@ -4,7 +4,7 @@
 		"lib": [
 			"ES2020"
 		],
-		"module": "node12",
+		"module": "node16",
 		"checkJs": true,
 		"noEmit": true
 	}

build/npm/update-all-grammars.mjs

@@ -6,7 +6,7 @@
 import { spawn as _spawn } from 'child_process';
 import { readdirSync, readFileSync } from 'fs';
 import { join } from 'path';
-import url from 'url'
+import url from 'url';
 
 async function spawn(cmd, args, opts) {
 	return new Promise((c, e) => {
@@ -20,7 +20,7 @@ async function main() {
 
 	for (const extension of readdirSync('extensions')) {
 		try {
-			let packageJSON = JSON.parse(readFileSync(join('extensions', extension, 'package.json')).toString());
+			const packageJSON = JSON.parse(readFileSync(join('extensions', extension, 'package.json')).toString());
 			if (!(packageJSON && packageJSON.scripts && packageJSON.scripts['update-grammar'])) {
 				continue;
 			}