Add EmptyStringDictionary

Author: mythz

src/ServiceStack.Text/TypeConstants.cs

@@ -19,6 +19,8 @@ public static class TypeConstants
 
         public static readonly byte[][] EmptyByteArrayArray = new byte[0][];
 
+        public static readonly Dictionary<string, string> EmptyStringDictionary = new Dictionary<string, string>(0);
+
         public static readonly List<string> EmptyStringList = new List<string>(0);
         public static readonly List<long> EmptyLongList = new List<long>(0);
         public static readonly List<int> EmptyIntList = new List<int>(0);