feat(comments): add Cusdis support (#43)

* feat(comments): add Cusdis support

* feat: set cusdis theme

assets/sass/components/_comments.scss

@@ -1,3 +1,7 @@
 .disqus-container {
     padding-top: 2rem;
+}
+
+#cusdis_thread {
+    padding-top: 2rem;
 }

layouts/partials/comments/provider/cusdis.html

@@ -0,0 +1,19 @@
+<div id="cusdis_thread" data-host="https://cusdis.com"
+        data-app-id="{{ .Site.Params.comments.cusdis.id }}"
+        data-page-id="{{ .File.UniqueID }}"
+        data-page-url="{{ .Permalink }}"
+        data-page-title="{{ .Title }}"></div>
+<script async defer src="https://cusdis.com/js/cusdis.es.js"></script>
+
+<script>
+    function setCusdisTheme(theme) {
+        let cusdis = document.querySelector('#cusdis_thread iframe');
+        if (cusdis) {
+            window.CUSDIS.setTheme(theme)
+        }
+    }
+
+    window.addEventListener('onColorSchemeChange', (e) => {
+        setCusdisTheme(e.detail)
+    })
+</script>