Support for the `@mixin` tag

[ddanielou]

Hi,

Thanks for this tool. Just tried it out on our codebase and it was a breeeze. I'm unfortunately getting a ton of errors because of our use of the @mixin tag.

Could this be supported?

Example

class Data
{
    public string $property = 'test';
}

/**
 * @mixin Data
 */
class DataProxy
{
   public function __get(string $name) {
       return new Data()->$name;
   }
}

{% types data: DataProxy %}

{{ data.property }} {# shouldn't error #}