iframe in – rewrite results – Override the output of this field with custom text

I’m trying to make a view for showing latest youtube videos in a block

I have a field called Youtube Video ID (Plain text) where I Drupal 8 stores the ID of the video…

I’m using the option of the field “Override the output of this field with custom text” in REWRITE RESULTS…

I’m doing something like this:

    <div class='embed-container-youtube'>
    <iframe src='http://www.youtube.com/embed/{{ field_id_video_de_youtube__value }}' frameborder='0' allowfullscreen></iframe>

Like you can see.. I’m using that mark up to show a youtube video.. taking the value of the field….

the problem is that Drupal is cleaning the iframe mark up.. I think for security…

this is how Drupal render it in the website

    <div class="embed-container-youtube">

When you configure the content type you can see a note:

“Allowed HTML tags:

 <del> <em> <i> <ins> <pre> <q> <small> <span> <strong> <sub> <sup> <tt> <ol> <ul> <li> <p> <br> <img>
    This field supports tokens."
how can I add more allowed tags?

How can I allow that HTML tag for this view?

I also tried to create an override for the template: 

in themes/my_theme/templates/block--views-block--ultimos-videos‌​-block-1.html.twig
but I cant print tags like this: {{ content.field_id_video_de_youtube }} The only available tag is {{ content}}


Drupal version: 

Source: https://www.drupal.org/taxonomy/term/3/feed