Added FileStream overload for appending attachments

FitConnect/SubmissionBuilder.cs

@@ -89,6 +89,9 @@ public interface ISubmissionWithData {
     ISubmissionWithData WithAttachments(params Attachment[] attachments);
     ISubmissionWithData WithAttachments(List<Attachment> attachments);
 
+    ISubmissionWithData WithAttachments(string fileName, string description, string mimeType,
+        FileStream content);
+
 
     SendableSubmission Build();
 }