Add cascade attribute for cascade data autoloading

[jacksleight]

Statamic cascade data is currently only available during the initial component render, it is not available in update renders.

This PR adds a new Cascade attribute that can be applied to the component class to enable autoloading of cascade data in the components view during all renders.

The implementation mirrors the @cascade Blade directive (https://statamic.dev/blade#cascade-directive). You can specify an array of cascade variables to include, fallback values if variables are missing, or exclude the array to load everything. Specifying a missing variable with no fallback will throw an exception.

use MarcoRieser\Livewire\Attributes\Cascade;

#[Cascade]
class Listing extends Component
{
    // ...
}

use MarcoRieser\Livewire\Attributes\Cascade;

#[Cascade([
	'homepage',
	'my_globals' => [],
])]
class Listing extends Component
{
    // ...
}

The attribute has no effect in Blade views.

[marcorieser]

Brilliant, thanks! ❤️ I'll give it a test and merge it afterwards.