Add an autoloading system to to Capsules

[antonioribeiro]

Description

This PR adds that ability for Capsules to autoload files, like a helpers.php:

<?php

return [
    'seo' => ['enabled' => true],

    'autoload' => [
        'files' => [__DIR__ . '/../Base/helpers.php'],
    ],
];

In the future, maybe, this could be done by using Composer itself, but I have the impression it would drag everyone feet if we have to always go back to Composer.json to add stuff.

What this doesn't solve is a possible Capsule need to override a Laravel helper (or any other package), as files are being loaded too late on the application lifecycle.

This is, of course, a very rudimentary autoloading system. 😆