Force use of ExperimentalAttribute with resource key

Author: Vogel612

Rubberduck.Parsing/Common/ExperimentalAttribute.cs

@@ -5,12 +5,15 @@ namespace Rubberduck.Parsing.Common
     [AttributeUsage(AttributeTargets.Class)]
     public class ExperimentalAttribute : Attribute
     {
-        public ExperimentalAttribute() : this(string.Empty)
-        {
-        }
-
         public ExperimentalAttribute(string resource)
         {
+            Resource = resource;
         }
+
+        /// <summary>
+        /// Resource key to look up in <see cref="Rubberduck.Resources.Experimental.ExperimentalNames"/>.
+        /// Also serves as a unique identifier to distinguish experimental features from one another.
+        /// </summary>
+        public string Resource { get; }
     }
 }