Mantra Theme Branding

mantra_theme.libraries.yml

branding:
  css:
    component:
      css/drupal/component/branding.css: {}

branding.css

.site-name {
    font-size: large;
    font-weight: bold;
    text-decoration: none;
}

block--system-branding-block.html.twig

Copy from system template.

Attach mantra_theme/branding library.

Add site-name, site-logo classes.

{% block content %}
  {{ attach_library('mantra_theme/branding') }}
  {% if site_logo %}
    <a class="site-name" href="{{ path('<front>') }}" rel="home">
      <img class="site-logo" src="{{ site_logo }}" alt="{{ 'Home'|t }}" />
    </a>
  {% endif %}
  {% if site_name %}
    <a class="site-name" href="{{ path('<front>') }}" rel="home">{{ site_name }}</a>
  {% endif %}
  {{ site_slogan }}
{% endblock %}