feat: Implement tap() method for instance manipulation

[rabrowne85]

Problem

Pest Plugin Browser currently doesn’t provide a straightforward way to extend the Webpage class with custom, test-specific behaviours.

For example, consider the need to apply padding to an element before taking a screenshot. Right now, this requires verbose and repetitive script() calls in every test:

visit('/')
    ->assertSee('Something')
    ->script("
        const el = document.querySelector('[data-test=\"some-button\"]');
        if (el) {
            el.dataset.originalStyle = el.getAttribute('style') || '';
            el.style.padding = '0.75rem';
        }
    ")
    ->screenshotElement('[data-test="some-button"]', 'some-button')
    ->script("
        const el = document.querySelector('[data-test=\"some-button\"]');
        if (el && el.dataset.originalStyle !== undefined) {
            el.setAttribute('style', el.dataset.originalStyle);
            delete el.dataset.originalStyle;
        }
    ");

This quickly becomes unwieldy across multiple tests.

Unlike Laravel Dusk (which supports macros on the Browser class), there's no current mechanism in Pest Plugin Browser to extend Webpage's behaviour locally.

Proposed Solution

This PR introduces a tap() method to the Webpage class, enabling users to perform inline actions on the current page context - without breaking the fluent chain.

This unlocks clean, composable test logic. For example:

visit('/')
    ->assertSee('Something')
    ->tap(fn ($page) => screenshotElementWithPadding($page, '[data-test="some-button"]', 'some-button'));

Here's how the helper might look in Pest.php:

function screenshotElementWithPadding(
    Webpage $page,
    string $selector,
    string $filename,
): void {

    $page->script("
        const el = document.querySelector('$selector');
        if (el) {
            el.dataset.originalStyle = el.getAttribute('style') || '';
            el.style.padding = '0.75rem';
        }
    ");

    $page->screenshotElement($selector, $filename);

    $page->script("
        const el = document.querySelector('$selector');
        if (el && el.dataset.originalStyle !== undefined) {
            el.setAttribute('style', el.dataset.originalStyle);
            delete el.dataset.originalStyle;
        }
    ");
}

[jonnywilliamson]

That's clever and simple!