site/_src/_includes/menu-footer.html

<nav class="menu menu--footer">

    <div class="grid grid--full grid-medium--half">
        <div class="grid__col">
            {% for link in site.data.menus.main %}

                {% assign active = nil %}
                {% if page.url contains link.url %}
                    {% assign active = 'active' %}
                {% endif %}

                <a class="menu__link {{ active }}" href="{{ link.url }}">{{ link.title }}</a>

            {% endfor %}
        </div>

        <div class="grid__col">
            {% for link in site.data.menus.footer %}

                {% assign active = nil %}
                {% if page.url contains link.url %}
                    {% assign active = 'active' %}
                {% endif %}

                <a class="menu__link {{ active }}" href="{{ link.url }}">{{ link.title }}</a>

            {% endfor %}
        </div>
    </div>

</nav>