feat: explicit resource management

[xbwwj]

Add explicit resource management, so that users can use using statement instead of boilerplate and forgettable try-finally:

import { createSession } from 'wreq-js';

// original try-finally
const session = await createSession({ browser: 'chrome_142', os: 'windows' });
try {
  await session.fetch('https://example.com/a');
} finally {
  await session.close();
}

// with EMR using statement
await using session = await createSession({ browser: 'chrome_142', os: 'windows' });
await session.fetch('https://example.com/a');

I'm not sure if tests are required as using is just a syntax sugar around the .close() method.