make endDate a property so it gets exported too

YahooAuctionsItem.cs

@@ -31,7 +31,7 @@ namespace Buypeeb {
 		public string notes { get; set; }
 		public bool favourite { get; set; } = false;
 		public DateTime startDate;
-		public DateTime endDate;
+		public DateTime endDate { get; set; }
 		public DateTime lastUpdated;
 		public int bids;
 		public bool autoExtension;