fix: mark FeedbackBase default constructor as obsolete

There are situations now where feedbacks in the feedback collection
can be used to update things on UIs. If the feedback doesn't have a key, it can't
be used for this purpose.

src/PepperDash.Essentials.Core/Feedbacks/BoolFeedback.cs

@@ -42,6 +42,7 @@ namespace PepperDash.Essentials.Core
         /// it will NOT reflect an actual value from a device until <seealso cref="FireUpdate"/> has been called
         /// </remarks>
         /// <param name="valueFunc">Delegate to invoke when this feedback needs to be updated</param>
+        [Obsolete("use constructor with Key parameter. This constructor will be removed in a future version")]
         public BoolFeedback(Func<bool> valueFunc)
             : this(null, valueFunc)
         {