Parse User Defined Attributes in WMarker.cs

As per the USFM Documentation:
https://ubsicap.github.io/usfm/attributes/index.html#user-defined-attributes

> Any user defined attributes must begin with the prefix x-.

USFMToolsSharp/Models/Markers/WMarker.cs

@@ -12,7 +12,7 @@ public class WMarker : Marker
     {
         public string Term;
         public Dictionary<string, string> Attributes;
-        private static Regex wordAttrPattern = new Regex("([\\w]+)=?\"?([\\w,:.]*)\"?", RegexOptions.Singleline);
+        private static Regex wordAttrPattern = new Regex("([\\w-]+)=?\"?([\\w,:.]*)\"?", RegexOptions.Singleline);
         public override string Identifier => "w";
 
         public override string PreProcess(string input)