Give each() callback access to foreach index

[MizouziE]

TL;DR: If a user callback has 2 parameters, use the second as the index

Working recently with the each() function we've thought it could be handy to have access to the index of the foreach in the case that we're expecting the same element but with different attributes/content. By allowing for the integer index to be passed into the callback, a user can use that to compare against an array of expectations.

A rough example:

    public function test_foo(): void
    {
        $this->component(Foo::class)
            ->assertElementExists(function (AssertElement $element) {
                $element->each('span', function (AssertElement $span, int $index) {
                    dump('index: ' . $index);
                    dump('span: ' . $span->getParser()->getContent());
                });
            });
    }

[sinnbeck]

Sounds like a good idea.