fix: giscus use current lang as default，and add missing loading params

layouts/partials/comments/provider/giscus.html

@@ -11,7 +11,8 @@
     data-emit-metadata="{{- default 0 .emitMetadata -}}"
     data-input-position="{{- default `top` .inputPosition -}}"
     data-theme="{{- default `light` .lightTheme -}}"
-    data-lang="{{- default `en` .lang -}}"
+    data-lang="{{- default $.Language.LanguageCode .lang -}}"
+    data-loading="{{- .loading -}}"
     crossorigin="anonymous"
     async
 ></script>