hugo-theme-stack/layouts/_markup/render-blockquote.html

{{ if eq .Type "alert" }}
    {{- $type := .AlertType -}}
    {{- $icons := site.Params.article.alertIcon -}}
    {{- $icon := index $icons $type -}}
    <blockquote class="alert alert-{{ $type }}">
        <div class="alert-header">
            <span class="alert-icon">
                {{- $icon -}}
            </span>
            <span class="alert-title">
                {{- with .AlertTitle -}}
                    {{ . }}
                {{- else -}}
                    {{ or (i18n (printf "article.alert.%s" $type)) (title $type) }}
                {{- end -}}
            </span>
        </div>
        <div class="alert-body">
            {{ .Text }}
        </div>
    </blockquote>
{{ else }}
    <blockquote>
        {{ .Text }}
    </blockquote>
{{ end }}