add youtube social media

im trying to add youtube social media icon on this theme, i edit the business_responsive_theme.theme and added the following:

function business_responsive_theme_form_system_theme_settings_alter(&$form, \Drupal\Core\Form\FormStateInterface $form_state) {
//Add Youtube
$form['business_responsive_theme_settings']['social_icon']['youtube_url'] = array(
'#type' => 'textfield',
'#title' => t('Youtube Link'),
'#default_value' => theme_get_setting('youtube_url'),
}
Also add the youtube variables in the function business_responsive_theme_preprocess_page(&$variables)
// Social media global variable.
$variables['show_social_icon'] = theme_get_setting('show_social_icon');
$variables['facebook_url'] = theme_get_setting('facebook_url');
$variables['google_plus_url'] = theme_get_setting('google_plus_url');
$variables['twitter_url'] = theme_get_setting('twitter_url');
$variables['linkedin_url'] = theme_get_setting('linkedin_url');
$variables['pinterest_url'] = theme_get_setting('pinterest_url');
//Add Youtube
$variables['youtube_url'] = theme_get_setting('youtube_url');
$variables['rss_url'] = theme_get_setting('rss_url');
$variables['copyright_text'] = theme_get_setting('copyright_text');
$variables['show_credit_link'] = theme_get_setting('show_credit_link');

Then add in page.html.twig

{% if youtube_url %}

{% endif %}

Then i go to admin/appearance/settings/business_responsive_theme and on the Social Media Link, I can see the Youtube Link and I added the youtube channel link then save it. however its not showing on the page. Is there anything i need to do?