add out of stock action cable

app/channels/out_of_stock_channel.rb

@@ -0,0 +1,10 @@
+class OutOfStockChannel < ApplicationCable::Channel
+  def subscribed
+    stream_from "out_of_stock_channel"
+  end
+
+  def unsubscribed
+  	stop_all_streams
+    # Any cleanup needed when channel is unsubscribed
+  end
+end