Explicitly require logger

…to address uninitialized constant
ActiveSupport::LoggerThreadSafeLevel::Logger issue.

Author: ur5us

lib/public_activity.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require 'active_support'
+require 'logger'
 require 'action_view'
 # +public_activity+ keeps track of changes made to models
 # and allows you to display them to the users.