Add extensions service and routes

src/utils/list-folders.ts

@@ -0,0 +1,25 @@
+import fs from 'fs';
+import path from 'path';
+import { promisify } from 'util';
+import APIError, { ErrorCode } from '../error';
+
+const readdir = promisify(fs.readdir);
+const stat = promisify(fs.stat);
+
+export default async function listFolders(location: string) {
+	const fullPath = path.join(process.cwd(), location);
+	const files = await readdir(fullPath);
+
+	const directories: string[] = [];
+
+	for (const file of files) {
+		const filePath = path.join(fullPath, file);
+		const stats = await stat(filePath);
+
+		if (stats.isDirectory()) {
+			directories.push(file);
+		}
+	}
+
+	return directories;
+}