add lang option

config.yaml

@@ -95,6 +95,7 @@ params:
             darkTheme:
             reactionsEnabled: 1
             emitMetadata: 0
+            lang:
 
         gitalk:
             owner:

layouts/partials/comments/provider/giscus.html

@@ -9,6 +9,7 @@
     data-reactions-enabled="{{- default 1 .reactionsEnabled -}}"
     data-emit-metadata="{{- default 0 .emitMetadata -}}"
     data-theme="{{- default `light` .lightTheme -}}"
+    data-lang="{{- default `en` .lang -}}"
     crossorigin="anonymous"
     async
 ></script>