fix: browser profile leak

[szmarczak]

Fixes #32

Tested manually via:

const { BrowserPool, PlaywrightPlugin, PuppeteerPlugin } = require('.');
// const playwright = require('playwright');

const browserPool = new BrowserPool({
    browserPlugins: [new PlaywrightPlugin(require('playwright').chromium)],
});

console.time('x');

// An asynchronous IIFE (immediately invoked function expression)
// allows us to use the 'await' keyword.
(async () => {
    console.timeLog('x', 'before new page');
    // // Launches Chromium with Playwright and returns a Playwright Page.
    const page1 = await browserPool.newPage();
    console.timeLog('x', 'after new page');
    // // You can interact with the page as you're used to.
    // await page1.goto('https://example.com');
    // // When you're done, close the page.
    await page1.close();
    console.timeLog('x', 'after page close');
    // // Opens a second page in the same browser.
    // const page2 = await browserPool.newPage();
    // When everything's finished, tear down the pool.
    await browserPool.destroy();
    console.timeLog('x', 'after pool destroy');

    console.log(process._getActiveHandles().length);
    process.exit();
})();