Add support for inheritance in #[Friend]

[alek-as]

The library works very well for most of our use cases, thank you for creating it!

We've recently discovered that adding #[Friend] annotation with an interface as friend class will produce an error when the method is called from implementation classes.

See below for simple code snippet:

<?php

declare(strict_types=1);

namespace App;

use DaveLiddament\PhpLanguageExtensions\Friend;

interface Foo
{
}

class Bar
{
    #[Friend(Foo::class)]
    public function bar(): void
    {
    }
}

class Baz implements Foo
{
    public function baz(): void
    {
        $bar = new Bar();

        $bar->bar();
    }
}

Produced error:

------ ----------------------------------------------------------------------------------------------- 
  Line   src/Foo.php                                                                                    
 ------ ----------------------------------------------------------------------------------------------- 
  27     App\Bar::bar cannot be called from App\Baz, it can only be called from its friend(s): App\Foo  
 ------ -----------------------------------------------------------------------------------------------

Is this error intentional?