Add very basic but functional support for authentication and custom servers

ntfysh_client/SubscribedTopic.cs

@@ -0,0 +1,23 @@
+using System.IO;
+
+namespace ntfysh_client
+{
+    public class SubscribedTopic
+    {
+        public SubscribedTopic(string topicId, string serverUrl, string username, string password, StreamReader stream)
+        {
+            TopicId = topicId;
+            ServerUrl = serverUrl;
+            Username = username;
+            Password = password;
+            Stream = stream;
+        }
+
+        public string TopicId { get; }
+        public string ServerUrl { get; }
+        public string Username { get; }
+        public string Password { get; }
+
+        public StreamReader Stream { get; }
+    }
+}