Camel case underscore as well (#1082)

Fixed the issue where the Archive helper camel cases post_type to Post_type, different to the customizer that camel cases it to PostType.

library/Helper/Archive.php

@@ -34,7 +34,7 @@ public static function getArchiveProperties(string $postType, object $customize)
      */
     public static function camelCasePostTypeName($postType)
     {
-        return str_replace(' ', '', ucwords(str_replace('-', ' ', $postType)));
+        return str_replace(' ', '', ucwords(str_replace(['-', '_'], ' ', $postType)));
     }
 
     /**