docs: Add example (#791)

Author: manisha1997

examples/ListMessages.md

@@ -0,0 +1,21 @@
+```csharp
+using System;
+using Twilio;
+using Twilio.Base;
+using Twilio.Exceptions;
+using Twilio.Rest.Api.V2010.Account;
+
+class Program
+{
+    static void Main(string[] args)
+    {
+        TwilioClient.Init("TWILIO_ACCOUNT_SID", "TWILIO_AUTH_TOKEN");
+
+        var messages = MessageResource.Read(limit: 20);
+        foreach (var record in messages) {
+            Console.WriteLine(record.Body);
+        }
+    }
+}
+
+```