Add Rails webhook engine, docs, and dependency refresh

lib/yookassa.rb

@@ -7,6 +7,7 @@ require "yookassa/config"
 require "yookassa/payments"
 require "yookassa/refunds"
 require "yookassa/receipts"
+require "yookassa/webhooks"
 
 module Yookassa
   class << self
@@ -31,5 +32,11 @@ module Yookassa
     def receipts
       @receipts ||= Receipts.new
     end
+
+    def webhooks
+      @webhooks ||= Webhooks.new
+    end
   end
 end
+
+require "yookassa/railtie" if defined?(Rails::Railtie)