Add MatchedTransactionId field (#26)

Co-authored-by: Joshua Marble <[email protected]>

YNAB.Rest/Transaction.cs

@@ -44,6 +44,7 @@ public class Transaction
         public string CategoryName { get; set; }
         [JsonProperty(PropertyName = "subtransactions")]
         public IList<SubTransaction> SubTransactions { get; set; }
+        public string MatchedTransactionId { get; set; }
         [JsonConverter(typeof(StringEnumConverter))]
         public DebtTransactionType? DebtTransactionType { get; set; }