How to add custom email template

[AgnieszkaK]

I'm trying to create new order state in my module.

I want to add my custom email template to add it do this state, but code below searches $template_name in prestashop_app/mails location and I want it to use file with email template in my module

$pending = new OrderState();

            $pending->module_name =  $module_name;
            $pending->template = $template_name;
            $pending->unremovable =  $unremovable;
            $pending->color = $pending_color;
            $pending->send_email = $pending_send_email;
            $pending->paid = $pending_paid;