Improve Media Library to use max fize size value from config

[timoransky]

In our Media repository we extend spatie/laravel-medialibrary but our custom MediaCollection model is not taking into account value from config medialibrary.max_file_size.
The only way to use it is for now to set the value in the collection itself like so:

public function registerMediaCollections() {
    $this->addMediaCollection('Example')
        ...
        ->maxFilesize(config('medialibrary.max_file_size'));
}

The point of this issue is to somehow use the config value as the default one.

Link to repository: BRACKETS-by-TRIAD/media