Make the history recording optional.

src/invidious/config.cr

@@ -23,6 +23,7 @@ struct ConfigPreferences
   property listen : Bool = false
   property local : Bool = false
   property locale : String = "en-US"
+  property watch_history : Bool = true
   property max_results : Int32 = 40
   property notifications_only : Bool = false
   property player_style : String = "invidious"