Added availability check functions

[TavoNiievez]

$I->seePageIsAvailable() allows to do in a line of code what is normally done like this: [See source]

    public function testPublicBlogPost(): void
    {
        $client = static::createClient();
        $blogPost = $client->getContainer()->get('doctrine')->getRepository(Post::class)->find(1);
        $client->request('GET', sprintf('/en/blog/posts/%s', $blogPost->getSlug()));

        $this->assertResponseIsSuccessful();
    }

while $I->seePageRedirectsTo() allows to do in a line of code what is normally done in this way: [See source]

    public function testSecureUrls(string $url): void
    {
        $client = static::createClient();
        $client->request('GET', $url);

        $this->assertResponseRedirects(
            'http://localhost/en/login',
            Response::HTTP_FOUND,
            sprintf('The %s secure URL redirects to the login form.', $url)
        );
    }

[DavertMik]

Maybe we can take this into InnerBrowser so it would be available to all frameworks and php browser?
This doesn't seem to be Symfony related