fix(CrawlUrl): Use before initialization is now impossible

[Voltra]

Before this PR, it was possible to call \Spatie\Crawler\CrawlUrl::getId on an object with an uninitialized îd property:

$crawlUrl = CrawlUrl::create(
  url: $someUriObj,
  foundOnUrl: $foundOnUrl,
  linkText: "some text",
); // Here `$crawlUrl->id` is left uninitialized

// Here $crawlUrl is in a "constructed" but invalid state

$crawlUrl->getId(); // This throws an exception, unless the ID has been set externally before being called

This is because $id is type-annotated with mixed (which is the default any way) and the PHP manual says:

Typed properties must be initialized before accessing, otherwise an Error is thrown.

This PR fixes this issue

PS: It also introduces a minimally usable devcontainer configuration for Github codespaces and the like, this can be cherrypicked out

[freekmurze]

Could you add a test for this?

[Voltra]

Done

[freekmurze]

So of the tests are failing, could you take a look?

[Voltra]

Fixed, seems like describe was introduced after Pest 2.0.0

[freekmurze]

Thanks!