site/_includes/feedback.html

<!-- Send feedback function -->
<script>
function SendLinkByMail(href) {
var subject= "{{site.site_title}} feedback";
var body = "I have some feedback about the {{page.title}} page: ";
body += window.location.href;
body += "";
var uri = "mailto:{{site.feedback_email}}?subject=";
uri += encodeURIComponent(subject);
uri += "&body=";
uri += encodeURIComponent(body);
window.location.href = uri;
}
</script>

<li><a href="mailto:{{ site.data.project.dev_list }}" target="_blank"><i class="fa fa-envelope-o"></i> Feedback</a></li>