stub out yubico nfc support for ios

src/iOS/NFCReaderDelegate.cs

@@ -0,0 +1,54 @@
+using CoreNFC;
+using Foundation;
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Text.RegularExpressions;
+
+namespace Bit.iOS
+{
+    public class NFCReaderDelegate : NFCNdefReaderSessionDelegate
+    {
+        private Regex _otpPattern = new Regex("^.*?([cbdefghijklnrtuv]{32,64})$");
+        private Action<bool, string> _callback;
+
+        public NFCReaderDelegate(Action<bool, string> callback)
+        {
+            _callback = callback;
+        }
+
+        public override void DidDetect(NFCNdefReaderSession session, NFCNdefMessage[] messages)
+        {
+            var results = new List<string>();
+            foreach(var message in messages)
+            {
+                foreach(var record in message.Records)
+                {
+                    try
+                    {
+                        results.Add(new NSString(record.Payload, NSStringEncoding.UTF8));
+                    }
+                    catch { }
+                }
+            }
+
+            foreach(var result in results)
+            {
+                Debug.WriteLine("READ TAG: " + result);
+                if(_otpPattern.IsMatch(result))
+                {
+                    Debug.WriteLine("TAG IS MATCH: " + result);
+                    _callback.Invoke(true, result);
+                    return;
+                }
+            }
+
+            _callback.Invoke(false, "No tags were read.");
+        }
+
+        public override void DidInvalidate(NFCNdefReaderSession session, NSError error)
+        {
+            _callback.Invoke(false, error?.LocalizedDescription);
+        }
+    }
+}