Add some styling to non-field-errors

[EdoStorm96]

Currently in form_template.html, non-field errors receive basically no styling, which can cause some ugly results, when using these. It would be nice, if there is at least some simple styling for these.

My quick suggestion, is something like this:

    {% if errors %}
        <div class="uu-form-text-row mb-0">
            <div class="uu-form-text">
                <div class="alert alert-primary">
                    <ul class="mb-1">
                        {% for err in errors %}
                            <li>{{ err }}</li>
                        {% endfor %}
                    </ul>
                </div>
            </div>
        </div>
    {% endif %}

Which results, in something like this:

Maybe a nice starting point.