Update README

README.md

@@ -26,8 +26,8 @@ class RecipesController < ApplicationController
  string :quantity do |value|
  value =~ /\A\d+(?:\.\d+)g\z/
  end
- date :date, only: ["%Y/%m/%d", "%Y.%m.%d"]
- time :time, only: "%Y/%m/%d %H:%M:%S"
+ date :date, format: ["%Y/%m/%d", "%Y.%m.%d"]
+ time :time, format: "%Y/%m/%d %H:%M:%S"
  end
 
  def create
@@ -70,6 +70,7 @@ irb(main):005:0> app.post "/recipes", name: "alice", type: "bob"
 * except
 * handler
 * strong
+* format (only for date and time)
 
 ## Tips
 WeakParameters.stats returns its validation metadata, and this is useful for auto-generating API documents.