enable comments via utteranc.es

layouts/partials/scripts/utterances.html

@@ -0,0 +1,8 @@
+<script src="https://utteranc.es/client.js"
+        repo="{{ .Site.Params.utterancesRepo }}"
+        issue-term="og:title"
+        label="comments"
+        theme="github-light"
+        crossorigin="anonymous"
+        async defer>
+</script>