Converts icons script to esm

Attempts to improve perf will better parallel i/o

.fantasticonrc.js

@@ -1,6 +1,6 @@
 //@ts-check
 
-/** @type { import('@twbs/fantasticon').RunnerOptions} } */
+/** @type {import('@twbs/fantasticon').RunnerOptions} */
 const config = {
 	name: 'glicons',
 	prefix: 'glicon',

scripts/applyIconsContribution.js

@@ -1,22 +0,0 @@
-/* eslint-disable @typescript-eslint/no-var-requires */
-const fs = require('fs');
-
-// Update the icons contribution point in package.json
-const package = require('../package.json');
-const icons = require('../dist/icons-contribution.json').icons;
-if (JSON.stringify(package.contributes.icons) !== JSON.stringify(icons)) {
-	package.contributes.icons = icons;
-	const packageJSON = `${JSON.stringify(package, undefined, '\t')}\n`;
-	fs.writeFileSync('./package.json', packageJSON);
-}
-
-fs.rmSync('./dist/icons-contribution.json');
-
-// Update the scss file
-const newScss = fs.readFileSync('./dist/glicons.scss', 'utf8');
-const scss = fs.readFileSync('./src/webviews/apps/shared/glicons.scss', 'utf8');
-if (scss !== newScss) {
-	fs.writeFileSync('./src/webviews/apps/shared/glicons.scss', newScss);
-}
-
-fs.rmSync('./dist/glicons.scss');

scripts/applyIconsContribution.mjs

@@ -0,0 +1,32 @@
+import fs from 'fs';
+
+const packageJSONPromises = Promise.all([
+	import('../package.json', { assert: { type: 'json' } }),
+	import('../dist/icons-contribution.json', { assert: { type: 'json' } }),
+]);
+
+const scssPromises = Promise.all([
+	fs.promises.readFile('./dist/glicons.scss', 'utf8'),
+	fs.promises.readFile('./src/webviews/apps/shared/glicons.scss', 'utf8'),
+]);
+
+let pending = [];
+
+// Update the icons contribution point in package.json
+const [{ default: packageJSON }, { default: icons }] = await packageJSONPromises;
+
+if (JSON.stringify(packageJSON.contributes.icons) !== JSON.stringify(icons.icons)) {
+	packageJSON.contributes.icons = icons;
+	const json = `${JSON.stringify(packageJSON, undefined, '\t')}\n`;
+	pending.push(fs.promises.writeFile('./package.json', json));
+}
+
+// Update the scss file
+const [newScss, scss] = await scssPromises;
+
+if (scss !== newScss) {
+	pending.push(fs.promises.writeFile('./src/webviews/apps/shared/glicons.scss', newScss));
+}
+
+pending.push(fs.promises.rm('./dist/icons-contribution.json'), fs.promises.rm('./dist/glicons.scss'));
+await Promise.allSettled(pending);