fix: import from cjs (#476)

Closes https://github.com/microsoft/playwright-mcp/issues/456

index.js

@@ -15,5 +15,5 @@
  * limitations under the License.
  */
 
-import { createConnection } from './lib/index';
+import { createConnection } from './lib/index.js';
 export { createConnection };

tests/library.spec.ts

@@ -0,0 +1,27 @@
+/**
+ * Copyright (c) Microsoft Corporation.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import { test, expect } from './fixtures.js';
+import fs from 'node:fs/promises';
+import child_process from 'node:child_process';
+
+test('library can be used from CommonJS', { annotation: { type: 'issue', description: 'https://github.com/microsoft/playwright-mcp/issues/456' } }, async ({}, testInfo) => {
+  const file = testInfo.outputPath('main.cjs');
+  await fs.writeFile(file, `
+    const playwrightMCP = require('@playwright/mcp');
+    playwrightMCP.createConnection().then(() => console.log('OK'));
+ `);
+  expect(child_process.execSync(`node ${file}`, { encoding: 'utf-8' })).toContain('OK');
+});