support jsonify filter

lib/jekyll/filters.rb

@@ -1,4 +1,5 @@
 require 'uri'
+require 'json'
 
 module Jekyll
   module Filters
@@ -148,6 +149,15 @@ module Jekyll
       end
     end
 
+    # Convert the input into json string
+    #
+    # input - The Array or Hash to be converted
+    #
+    # Returns the converted json string
+    def jsonify(input)
+      input.to_json
+    end
+
     private
     def time(input)
       case input