Updated Definition format (markdown)

Definition-format.md

@@ -379,6 +379,12 @@ search:
     - path: xxx.php
       # only use it if we're searching for porn
       categories: [901, 902]
+  # [OPTIONAL] By default Cardigann removed any keys whose values resolve to Empty (or Null).
+  # This means that the key is not placed in the query string sent to the web site.
+  # However should the web site require that the empty key be present regardless, then set this parameter to true.
+  # Note that this does not apply to the special $Raw key, which is to say that keys built via $Raw are sent as is.
+  # Default is false.
+  allowEmptyInputs: true
   # list of HTTP arguments which are used by all paths
   inputs: 
     # Generate the category[] arguments list