chore: migrate to ESM (#303)

- [Why do I need `.js`
extension?](https://stackoverflow.com/a/77150985/6512681)
- [Why setting `rootDir` in the
`tsconfig.json`?](https://stackoverflow.com/a/58941798/6512681)
- [How to ensure that we add the `.js` extension via
ESLint](https://github.com/import-js/eslint-plugin-import/blob/main/docs/rules/extensions.md#importextensions)

Fixes https://github.com/microsoft/playwright-mcp/issues/302

src/transport.ts

@@ -18,7 +18,7 @@ import http from 'node:http';
 import assert from 'node:assert';
 import crypto from 'node:crypto';
 
-import { ServerList } from './server';
+import { ServerList } from './server.js';
 import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js';
 import { SSEServerTransport } from '@modelcontextprotocol/sdk/server/sse.js';
 import { StreamableHTTPServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js';