update `pandoc` data dir

pandoc/filters/resolve_internal_links.lua

@@ -20,8 +20,9 @@ return {
     local internal_link = l:clone()
     internal_link.target = ("#%s%s"):format(slug, anchor)
 
-    l.content = "↪"
+    l.content = "<->"
     l.target = ("%s.html#%s"):format(slug, anchor)
+    l.classes:insert("internal-next")
 
     return Inlines({ internal_link, l })
   end }